Source:https://websmp230.sap-ag.de/sap%28bD1lbiZjPTAwMQ==%29/bc/bsp/spn/sapnotes/index2.htm?numm=481906
Summary
Symptom
The following questions arise in connection with the integration of Supply Network Planning (SNP) and Production Planning and Detailed Scheduling (PP/DS):
SNP-PP/DS integration, documentation, FAQ, production horizon, PP/DS horizon, SNP->PP/DS
Reason and Prerequisites
Comparing SNP with PP/DS: SNP
The Role Of SNP
=================
SNP planning makes the decisions on tactical planning and source of supply determination. The strengths of SNP planning are: The selection of the source of supply taking into account the costs, and the determination of the approximate production date taking into account both the procurement costs and the storage costs. The result of the SNP planning is the answer to "What is produced, where and when?". The answer to "when" cannot be more precise than a planning period, and it does not take the sequence-dependent setup activity into account.
The SNP Optimizer
===================
The SNP optimizer performs cost-based optimization. The SNP optimizer creates a production plan in a way so that an objective function is as close to its minimum value as possible. The objective function is the weighted total of the following costs:
The SNP optimizer is therefore able to make the following decisions in particular:
The SNP optimizer determines the following:
The SNP optimizer works on the basis of periods. The sequence of orders within a planning period is not defined. This has the following consequences:
Setup In The SNP Optimization
===============================
SNP planning is period-based planning. SNP planning determines the production quantities for each period; it does not determine the sequence of production orders. Therefore, SNP planning cannot take into account the exact effort required for the setup.
Usually, setups in SNP optimization are only taken into account by a setup allowance. The attributable capacity of a resource available in SNP is reduced by the loss factor. This means that a part of the capacity is kept free for the setup. You can set the loss factor for mixed resources in the master data of the resource.
Using the modeling option for fixed resource consumptions in SNP, the SNP optimizer supports a simple lot size planning, which may also be performed across periods for APO Release 3.1. Lot size planning reduces setup costs by summarizing the orders for large lots. With cross-period lot size planning (APO Release 3.1), the setup statuses of the previous period are taken into account when a product is produced in the current period with the same plan. This lot size planning is used in industries where setup operations greatly influence the production costs. If setups play a major role, you should try to ensure that the setups are already taken into account in SNP. SNP then generates plans that represent a reliable template for planning in PP/DS.
Material Flow In SNP Optimization
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The period factor or bucket offset controls the modeling of the material flow in SNP. If the period factor is high, you can often produce two or more production levels in one bucket. The lead times on several production levels become shorter. However, the result may be too optimistic. If you wish to err on the side of caution, you must work with a period factor of zero, but this is at the expense of the lead time.
The period factor in the product master applies only to the SNP heuristic. The same function can be applied in SNP optimization using the bucket offset in the SNP optimization profile and in the PPMs and transportation lanes.
Model Size And Complexity
===========================
Due to the runtime and memory requirements of SNP optimization, we must also think about the model size and the model complexity. Creating an SNP production plan is an NP-completeness problem. IT theory has taught us that there is no known algorithm to guarantee finding an optimal solution for the problem in polynomial runtime. For more information on NP-completeness problems, we recommend that you read the following book by Michael R. Garey and David S. Johnson: "Computers and Intractability: A Guide to the Theory of NP-Completeness".
In the case of SNP optimization, a distinction must always be made between purely continuous models and models known as discrete models. If fixed lot sizes, minimum lots, or piecewise linear cost functions are to be taken into account, you will require a discrete model. In this case, the system must perform a mixed integral optimization.
The continuous models are primarily restricted because of the memory required. However, the required runtime of purely continuous models is linearly dependent on the model size and is generally non-critical as a result.
On the other hand, the solution of discrete models using a mixed integral optimization can be considerably more complicated. It is generally not possible to guarantee the global optimum under realistic CPU time targets. Instead, permitted and high-quality solutions must be found with acceptable runtimes. The runtime and memory requirement of SNP optimization depends on the number of the variables. The number of variables is therefore restricted. You require a variable for each production quantity or procurement quantity that you want to determine using SNP optimization. In other words, you require a variable for each location product for each planning period. The practical upper limit is approximately two (2) million continuous variables or 100,000 discreet variables.
The following is an example of a continuous model:
7,000 products * 5 locations * 52 weeks = 1,820,000.
This type of continuous model already belongs to the large optimization models. This means that we require 4GB RAM for this continuous model. If the problem is too large or too complex, it may be simplified as follows:
Restricting the model size is a considerable incentive for hierarchical production planning. In SNP planning, you often have to work on aggregated data in order to reduce the number of variables. Nevertheless, you should determine detailed production plans at a later stage. The detailed production plans are then created using PP/DS.
Advantages Of SNP Optimization
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Disadvantages Of The SNP Optimizer
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The SNP optimizer has the following restrictions:
The SNP optimizer is therefore particularly suited to medium to long-term planning. You generally have to use the SNP - PP/DS order conversion to convert the result of the SNP optimizer to PP/DS orders. One of the actions you can then perform in PP/DS planning is to determine the exact sequence for production orders.
The SNP Production Horizon
============================
SNP does not create any orders within the SNP production horizon. The SNP production horizon can therefore be used to divide the responsibilities for planning among Supply Network Planning (the order is outside the SNP production horizon) and Production Planning and Detailed Scheduling (the order is within the SNP production horizon).
SNP Plans
==========
An SNP plan is the basis for planning in-house production in SNP and is stored in APO as SNP PPM or SNP PDS. SNP planning is primarily designed to provide a plan outlining the resource and component requirements in advance, and it does not aim to provide an exact model of all technical options. SNP plans are therefore simpler than PP/DS plans. Mode linkage, cover, minimum and maximum intervals of relationships, and so on are not important in SNP planning and therefore cannot be maintained in the SNP PPM. Alternative modes must be modeled in SNP as alternative PPMs or alternative SNP PDSs. An SNP plan refers to planning in planning periods. The length of an activity cannot be less than a day. SNP permits "day" as the smallest planning period. You can therefore plan accurately to one day at the most. In contrast, PP/DS permits planning to the exact second.
Validity Of SNP Plans
==========================
Usually, the lot-size intervals of an SNP plan differ from the lot-size intervals of the corresponding PP/DS plan. Typically, the lot-size interval of the SNP plan should correspond to the maximum quantity that can be produced in a planning period, while the lot-size interval of the PP/DS plan should correspond to the maximum order size. If several orders can be produced in a planning period, the lot-size interval of the SNP plan is usually larger than the lot-size interval of the PP/DS plan. If production takes longer than an SNP planning period, the lot-size interval may be smaller in the SNP plan than in the corresponding PP/DS plan.
Comparing SNP with PP/DS: PP/DS
The Role Of PP/DS
==================
The strengths of PP/DS planning are its consideration of sequence-dependent setup activities and restrictions that apply to the generation of production orders that can be produced: complete bills of material (BOMs) and routings, inclusion of change statuses and configuration. It also guarantees feasibility with planning that is exact to the second, and so on.
In general, lot sizes cannot be optimized independently of the sequence of the production orders. Lot size optimization is therefore regarded as being a PP/DS task. However, since you quickly encounter calculation limits, PP/DS offers only limited help during lot size optimization.
The PP/DS Optimizer
====================
Up to an including SCM 5.1, the PP/DS optimizer cannot create any new orders, but it optimizes the date and time of production and resource assignment of operations with regard to the following criteria:
These criteria form part of the objective function. The objective function is the weighted total of the criteria mentioned above. Optimization determines a production plan in which the required result, for example, the minimum setup times or sequence optimization, is achieved as far as possible. For this, the system varies the start times and the resource assignments of the operations. The system then uses the set objective function to assess the production plans created in this way. The production plan that has the minimum value for the objective function is the result of the optimization.
Read Note 712066 for further and more recent information about the PP/DS optimizer and restrictions for the PP/DS optimizer.
The PP/DS Horizon
==================
PP/DS planning is carried out within the PP/DS horizon. PP/DS planning usually does not create orders outside the PP/DS horizon.
The following exceptions exist:
In APO Release 3.0, the PP/DS horizon is identical to the production horizon. In APO Release 3.1, the PP/DS horizon and the SNP production horizon may differ. If the PP/DS horizon is initial, the SNP production horizon is used as the PP/DS horizon. In this case, there is no overlap between the two horizons. If the PP/DS horizon is shorter than the SNP production horizon, the PP/DS horizon is extended to the SNP production horizon. The time axis does not have any area that is not planned by either PP/DS or SNP. However, the PP/DS horizon can also be longer than the SNP production horizon. In this case, there is an area on the time axis that is planned jointly by SNP and PP/DS.
PP/DS Plans
============
A PP/DS plan provides the basis for planning in-house production in PP/DS. PP/DS plans are stored either as PP/DS PDSs or as PP/DS PPMs. In PP/DS, the production process is described using activities that are linked through relationships. Several logically related activities form an operation. In discrete manufacturing, an operation is generally composed of setup activities and processes. In process industries, on the other hand, operations are often more complex. An operation in the process industry can therefore consist of activities such as mixing, stirring, heating, cooling and cleaning. The activities of one operation must not be interrupted by the activities of another operation. The switch for continuous reservation of the resource is set in the PPM. This feature is called "Cover". In the PDS, the Cover feature for the activities in an operation is always set automatically.
The activities of a PP/DS plan can be carried out on alternative resources. These are defined as a mode in the plan. Each mode can have a different duration. If an activity is carried out on a certain alternative resource, this can mean that subsequent activities must also be carried out on compatible resources. This is known as mode linkage. The simplest case of mode linkage is where setups and processes have to be executed on the same resource.
You require both components and resources to execute an activity. The component consumption of each activity is also defined in the PP/DS plan.
In APO, you can use PP/DS PPMs, iPPE models, or PDSs generated from R/3, as PP/DS plans. The PP/DS PPM or a PDS generated from R/3 is either a combination of an R/3 BOM and an R/3 routing, or a combination of an R/3 BOM and an R/3 recipe.
Do We Require Modes In PP/DS?
============================
SNP planning does not know the mode concept from PP/DS. The integration of PP/DS plans with SNP plans results in additional work if alternative modes are used in PP/DS. The amount of work involved can be reduced by not using alternative modes in PP/DS. However, the disadvantages of not using alternative modes in PP/DS are as follows:
Validity Of PP/DS Plans
============================
Usually, the lot-size intervals of an SNP plan differ from the lot-size intervals of the corresponding PP/DS plan. Typically, the lot-size interval of the SNP plan should correspond to the maximum quantity that can be produced in a planning period, while the lot-size interval of the PP/DS plan should correspond to the maximum order size. The maximum quantity that can be produced per order is usually defined by physical constraints (for example, the boiler size). A PP/DS planned order that is outside the valid lot-size interval cannot be produced.
SNP and PP/DS: Shared view of the planning situation
SNP is used to determine an optimal sourcing for the planning. The plan created by SNP must be detailed at a later stage. The aspects of planning that were not considered in SNP must be taken into account.
For example:
PP/DS is used for these. If you want to add details to the SNP production plan or execute it, you must transfer the SNP production plan to a PP/DS production plan.
If SNP planning and PP/DS planning are carried out in a shared planning version, this results in several interfaces between the two plans:
Fixing PP/DS Planned Orders In SNP Planning
====================================================
PP/DS receipt elements can be displayed for SNP, but these elements are fixed. The stocks and PP/DS receipt elements are read and offset against the existing requirements as part of an SNP heuristic or the SNP optimization. During this, it is irrelevant whether the requirements lie inside or outside the production horizon. As a result, requirements outside the production horizon may also be covered by receipt elements within the production horizon. In this case, SNP must create new SNP receipt elements only for the remaining uncovered requirements. SNP cannot change PP/DS receipt elements. SNP handles PP/DS receipt elements in the same way as it handles stocks. SNP planning is therefore unable to adjust PP/DS planned orders to a changed requirement situation.
PP/DS planned orders are fixed for SNP planning because they are processed using functions that SNP planning is unable to understand; for example, exact scheduling or the explosion of PP/DS plans. Even if unnecessary PP/DS orders are outside the PP/DS horizon, SNP planning cannot delete these orders.
Pegging
=======
The system creates pegging relationships between the product receipts and the product requirements regardless of whether the product receipts or the requirements involve SNP orders or PP/DS orders. This solves the following problems:
Mixed Resources
===============
Mixed resources allow SNP and PP/DS to have a shared view of the resource schedule. The capacity commitment from PP/DS orders is also displayed for SNP on mixed resources. For this, the PP/DS capacity commitment is converted to a bucket resource reservation.
Single-mixed resources correspond to single activity resources in the detailed scheduling. Multimixed resources correspond to multi-activity resources in PP/DS planning. In Supply Network Planning, mixed resources behave in the same way as normal bucket resources.
Mixed resources can serve their purpose only if the capacity requirements for the PP/DS planned order are approximately the same as the capacity requirements for the SNP planned order.
For PP/DS planned orders, a capacity requirement on the bucket resource is calculated from the capacity requirement on the single resource. As a result, PP/DS capacity requirements are also displayed in SNP. Finite SNP planning can create new planned orders within the SNP horizon if sufficient capacity is still available for SNP despite the capacity commitment caused by PP/DS planned orders. Since PP/DS planned orders are fixed for SNP planning, it is sufficient to simply reduce the capacity available for SNP by the portion consumed by PP/DS planned orders.
As of APO Release 3.1, single-mixed resources can be used to model block capacities for block planning in characteristics-dependent planning (CDP). If a mixed resource is used for block planning, it can no longer be used in SNP.
Integration Master Data: Resources
How Do I Set A Mixed Resource?
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In APO, you cannot convert a single-activity resource to a single-mixed resource. You cannot convert a multi-activity resource to a multimixed resource either. In this case, you must delete the old resource and create a new resource.
If the resources are transferred from the R/3 system, the resource type must be changed in the inbound interface of the APO system. (For more information, see Note 329733).
If the user exit for resources is used to create mixed resources from the R/3 system, the user exits for the objects that use the resources (especially PPM) must be adjusted. (For more information, see Note 321474).
Problem: Different Capacity Requirements In SNP And PP/DS
=======================================================
The bucket requirements of a mixed resource are calculated in the PP/DS planned order only so that SNP planning obtains an accurate picture about the reservation of the resource from the SNP view. SNP planning cannot plan the resource correctly if the capacity requirements differ.
Cause
=======
The system explodes the plan again when an SNP planned order is converted to a PP/DS planned order. During this, the capacity consumptions are determined again. If the bucket consumption in the PP/DS plan differs from the bucket consumption in the SNP plan, the capacity consumption of the orders generated from the plans also differ.
Solution
======
Ensure that the bucket consumption in the PP/DS plan is identical to the bucket consumption in the SNP plan. You will find the bucket consumptions in the PP/DS PPM and SNP PPM as follows: There is a navigation tree in the upper left part of the PPM maintenance screen. Open the operation and open the activity. Then open the mode and double-click the resource. If you use the PDS, you can use transaction /SAPAPO/CURTO_SIMU to display the bucket consumption.
In addition, the bucket consumptions in the PP/DS plan should correspond to the capacity requirements in PP/DS.
Example 1
==========
The available bucket capacity for our resource can be defined as follows: Capacity=1,000 pieces per week. The resource is a single-activity resource that works 40 hours per week. An order of 100 pieces requires four hours in PP/DS and reserves 100 pieces of the available bucket capacity. As a result, the bucket consumption is 100 pieces. You define the variable duration of four hours/100 pieces in the mode of the PPM. You define the variable bucket consumption in the resource chart of the PPM.
Example 2
==========
The comparison of SNP capacity consumptions and PP/DS capacity consumptions becomes especially intuitive if the available bucket capacity (and therefore, the bucket consumption) is defined in a time unit. The available bucket capacity can be defined as 40 hours per week. The resource is a single-activity resource that works 40 hours per week. An order of 100 pieces requires four hours in PP/DS and reserves four hours of the available bucket capacity. In this case, the bucket consumption is four hours. You define the variable duration of four hours/100 pieces in the mode of the PPM. You define the variable bucket consumption of four hours in the resource chart of the PPM. This seems to be an unnecessary duplicate entry. However, as example 1 shows, this is not the case because the dimension of the bucket consumption does not have to be a time unit.
Connection Between The Duration And Capacity Consumption
======================================================
As the above example shows, the durations in the mode and the bucket consumption must be consistently defined in the PP/DS plan. If this is not the case, incorrect bucket consumptions are calculated for PP/DS planned orders. In the SNP plan, there is no connection between the duration and the bucket consumption. The reason for this is the different scheduling in SNP and PP/DS. The duration in the mode of a PP/DS plan basically describes the pure production time. The queue times between the activities result from the resource availability or the relationships. On the other hand, the lead time including the queue times is contained in the mode of an SNP plan. As a result, there is no direct connection between the duration and the bucket requirement in SNP.
Fixed Capacity Consumptions
=========================
Fixed capacity consumptions are usually used to roughly model setup activities. Setup activities are required between orders that produce different products. SNP does not perform order-specific planning. Instead, the SNP plan acts as a form of data storage. SNP actually plans quantities for each time interval (bucket). Therefore, fixed capacity consumptions must be dealt with carefully. This applies in particular as of APO Release 3.1. As of APO Release 3.1, you can split the quantities planned by SNP during the conversion from SNP to PP/DS (according to the fixed or maximum lot size in the product master or the lot-size intervals in PPM). The fixed bucket requirement in PP/DS multiplies as a result of these splits. As a result, the differences between the SNP capacity consumption and PP/DS capacity consumption increase.
Available Capacity In SNP And PP/DS
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If you have mixed resources, you can calculate the available bucket capacity from the continuous available capacity. However, you must bear in mind that part of the capacity in continuous PP/DS planning is required for the setup activity. As a result, the bucket capacity is generally a little smaller than the continuous capacity. The loss factor in the resource maintenance is available for this.
The loss factor must first be defined at random. The bucket capacity determined in this way therefore does not correspond exactly to the continuous capacity of the mixed resource. As a result, it is not guaranteed that a finite SNP plan created using the SNP optimizer, for example, can also be converted to a finite PP/DS plan.
You can check the accuracy of the bucket capacities only by analyzing the results of PP/DS planning and comparing them with SNP planning. If the PP/DS planned orders generate overloads on the continuous capacities (and these did not exist in SNP planning), the setup sequence is either poor or the bucket capacity is too high. If there is sufficient unused capacity in the PP/DS (which is not visible in SNP), we can assume that the bucket capacity is too low.
Even if this type of capacity control is considered to be important if the overall process is to work over a long period of time, we advise against having excessive accuracy requirements. With sequence-dependent setup activities, the capacity requirements on the continuous resource constantly change every time the sequence of production orders changes. The bucket capacities should not be changed every time for SNP. Capacity overloads and underloads of 10% are certainly tolerable.
Master data integration: PPM
You can either create SNP PPMs manually, or you can create them from PP/DS PPMs using a generation report. The integration of SNP planning and PP/DS planning requires the following:
SNP PPM and the corresponding PP/DS PPM can only claim to describe the same process if the following conditions are met:
The best way of meeting these requirements is to use the SNP PPM generation from PP/DS PPMs. Otherwise, you must ensure that both PPMs describe the same processes from an organizational point of view.
Generated SNP PPMs
===================
SNP PPMs can be generated from PP/DS PPMs. During this, the bucket consumption of the SNP PPM is determined from the mode durations of the PP/DS PPM. We can therefore assume that the available bucket capacity of the resource has the "time" dimension.
In Release 3.0, the variable SNP bucket consumption consists of the variable bucket consumption and the fixed bucket consumption of the PP/DS PPM. When determining the variable SNP bucket consumption, the variable consumptions of the output product and the maximum lot size of the PP/DS PPM are also taken into account. The fixed SNP bucket consumption is not supported in Release 3.0. The fixed duration in the SNP PPM is determined from the duration of an SNP planned order for a bucket size. However, a user can use a user exit to maintain the bucket consumptions and the duration in SNP PPM. In this case, the user is responsible for the consistent maintenance of the bucket consumption within the PP/DS PPM.
Generating The SNP PPM
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Refer to Notes 516260 and 323884.
Determining The Capacity Requirement
=================================
In addition to defining the duration, you must also define the bucket consumption for a mode when maintaining a PP/DS PPM with a mixed resource. This bucket consumption is transferred to the SNP PPM as a capacity consumption. The bucket consumption does not have to be defined in the "time" dimension. However, the conversion is especially simple if the bucket consumption has the "time" dimension. The PP/DS mode duration must be the same as the bucket consumption.
You are not permitted to maintain a variable duration and a variable capacity consumption in the PP/DS if you have multimixed resources. Both capacity requirement dimensions would depend on the quantity. This would lead to a quadratic dependence on the quantity for the bucket consumption. This cannot be modeled in the SNP PPM.
Mapping Alternative Modes
=================================
The generation report for SNP PPMs enables you to generate a specific number of SNP PPMs from different mode combinations contained in a PP/DS plan (SNP PPM generation with a lot size margin). The number of SNP PPMs depends on the number of activities and alternative modes of the PP/DS PPM.
In turn, SNP PPM generation without lot size margins means that exactly one SNP PPM is generated from a PP/DS PPM for a single lot size and a mode combination.
Determining The Mode Durations
===========================
SNP planning only roughly considers the durations of operations or activities. Only bucket resources are reserved in SNP. This does not depend on the duration of an activity. If, however, the SNP plan has several operations, the resources should be reserved for the correct planning periods. If the first operation of an order lasts longer than a planning period, the second operation must be scheduled in a planning period at a later stage. This shift is calculated using the mode durations in the SNP plan. The SNP PPM mode durations differ from the PP/DS PPM mode durations in the following aspects:
When generating without a lot size margin, the fixed duration is calculated as follows:
For each day that is started and that requires an activity, the fixed duration is increased by one day.
When generating with a lot size margin, the system bundles the maximum number of activities that fit in a bucket (these may be all operations if you have a monthly bucket). The fixed duration of the mode is then set to one day. The bucket consumptions result from the durations of the corresponding mode.
The logic is as follows: During the SNP PPM generation without a lot size margin, a new operation is generated if the primary resource changes from one bucket to another. A new activity is generated if a secondary resource or a material changes.
During the generation with a lot size margin, the system merges as many PPDS activities for an SNP activity as the bucket specification allows. This means: If weekly buckets are used during the generation, a much larger number of activities fit into a bucket (and are therefore merged for the SNP activity) than if daily buckets were used for the SNP PPM generation.
Determining The Component Quantities
=================================
The following applies to SNP PPM generation without a lot size margin:
The variable consumptions from the PP/DS PPM are multiplied by the lot size from the initial screen for the SNP PPM generation and they are added to the fixed consumption quantity. The result is transferred to the SNP PPM as a variable quantity. The SNP PPM generation without a lot size margin cannot represent a fixed material consumption.
Linking SNP PPMs With PP/DS PPMs
========================================
The SNP plan can be linked to a PP/DS plan. This means that the system does not find any random PP/DS sources of supply when SNP orders are converted to PP/DS orders, but it creates the PP/DS orders using the PP/DS PPM that is linked to the SNP PPM.
Manually created SNP plans (PPMs) may also be linked to existing PP/DS plans (PPMs). In this case, however, the user must ensure that the manual maintenance is a logical representation and creates a correct relationship between the two plans (PPMs).
Quantity Split During Conversion
==============================
The conversion from SNP to PP/DS also entails a change in the planning semantics from the quantities per planning period that are planned in SNP to orders. You cannot expect lot sizes to be transferred 1:1 during this change. With APO Release 3.1, you can therefore split the lot size during the conversion. If several fixed lots or lots with a maximum quantity are produced in an SNP planning period, the split can be performed by noting the maximum quantities from the product master or the maximum quantities of the lot size intervals in the PP/DS PPM. The conversion creates several smaller orders with suitable lot sizes.
Selecting A Different PP/DS PPM
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If you want the lot sizes to be retained (for example, if we use weekly planning periods in SNP, we also have weekly lot sizes in PP/DS), we can search for a suitable PP/DS PPM during the conversion. This is the case if you do not set the "Use SNP sources of supply" switch on the initial screen of the conversion report.
PDS Master Data Integration
The SNP PDS is not generated from a PP/DS PDS; instead, it is generated directly from R/3 or from an iPPE. This has the following advantages:
Although these advantages exist, there are also some disadvantages:
Determining The Capacity Requirement
=================================
During the transfer from R/3 to SCM, the capacity requirements of the SNP PDSs are determined by the default implementation of the BAdI /SAPAPO/CURTO_SNP as follows: If the bucket resource has the "time" dimension, the capacity requirement is copied from the duration of the R/3 operation. If you have different dimensions for the available capacity for the bucket resource, the BAdI must be implemented differently, or you must maintain the capacity requirements manually in R/3. This option is available as of SCM Release 5.0. It is provided by transaction PDS_MAINT.
Determining Mode Durations
==========================
SNP planning only roughly considers the durations of operations or activities. Only bucket resources are reserved in SNP. This does not depend on the duration of an activity. If, however, the SNP plan has several operations, the resources should be reserved for the correct planning periods. If the first operation of an order lasts longer than a planning period, the second operation must be scheduled in a planning period at a later stage. This shift is calculated using the mode durations in the SNP plan. The required mode durations in SNP PDS must therefore differ from the mode durations in PP/DS PDS as follows:
As of SCM Release 5.0, you can maintain the SNP mode durations in R/3 manually using transaction PDS_MAINT. In lower releases, the mode durations of SNP PDSs can be changed only using a BAdI. To do this, use one of the following BAdIs:
Transferring SNP planning to the PP/DS production plan
The result of the SNP optimizer provides a plan that is finite at planning period level. However, overloads may still occur within the planning periods and for sequence-dependent setup activities. These must be corrected in PP/DS planning.
To plan the result in PP/DS planning in detail, the SNP optimization result must be transferred to a PP/DS production plan. Often, only the most important components are planned in SNP. Therefore, PP/DS must also generate complete planned orders (planned orders with all components and all required activities and resource reservations). These orders can then be used to determine the detailed dates/times and the order sequence taking into account the sequence-dependent setup activity.
The following options exist for transferring the SNP production plan to a PP/DS production plan:
The problem of advance production
The requirement of a product is often subject to strong seasonal fluctuations. If there are insufficient capacities within a period, the SNP optimizer or capacity leveling can shift the production to a previous period. In this period, the total number of product requirements is smaller than the total number of receipt elements planned by SNP. If this period moves to the PP/DS horizon and a PP/DS heuristic is executed, the PP/DS heuristic may adjust the receipt elements in the PP/DS horizon to the product requirements, that is, they are reduced. This destroys the stock build-up planned by SNP. At the height of the season, it is no longer possible to create sufficient receipt elements.
Therefore, one criterion for evaluating the procedures for the integration of SNP to PP/DS is the way in which the procedure supports advance production.
SNP->PP/DS conversion
First, the conversion is discussed. If you use this procedure, SNP is used to create all of the planned orders. The SNP planned orders are converted to PP/DS planned orders in a conversion process. This results in the following planning process:
Procedure
===========
You use transaction /SAPAPO/RRP_SNP2PPDS or the report /SAPAPO/RRP_SNP2PPDS to convert the SNP receipt elements in the PP/DS horizon to PP/DS receipt elements.
The quantities of PP/DS receipt elements are no longer changed after the conversion. No procurement planning heuristics are executed in the PP/DS. Of course, you can continue to use all procedures of detailed scheduling and all procedures used for the transfer to Execution for the PP/DS receipt elements. You can therefore use the PP/DS optimizer to schedule and reschedule the PP/DS receipt elements. You can execute DS heuristics. The PP/DS planned order can be rescheduled in the graphical planning table. This planned order can be checked using an ATP check and the conversion to a production order can be triggered in APO.
Settings
==============
This procedure requires the following settings:
Setting The Horizons
=========================
As of APO Release 3.1, you can select a PP/DS horizon that is larger than the production horizon. This can be put to good use here. Set a very small production horizon. This also enables SNP planning to create new planned orders in the short-term area. These new planned orders may soon have to be converted to PP/DS planned orders so that they are correctly sorted into the setup sequence. The PP/DS horizon is relevant for this. The PP/DS horizon can be larger than the SNP production horizon.
Strategy Profile For SNP->PP/DS Order Conversion
========================================================================
The purpose of the conversion is to transfer SNP planning results to PP/DS planning as accurately as possible. The system tries to adjust the PP/DS orders as closely as possible to the SNP planning requirements. The PP/DS orders are only scheduled during the conversion, but they are not planned. Heuristics, MRP ,or optimization can be used to plan the results after the conversion.
During the order conversion from SNP to PP/DS, the scheduling uses the start time or the end time from the period pattern of SNP planning (bucket).
With the "Backward" strategy setting, the system transfers the end time of a bucket and tries to schedule from the "Backwards" time towards today. During this, the working times of the resource are taken into account. If you have a finite resource and a finite strategy, the capacity utilization of the resources is also taken into account. If the working time of the resource is specified, for example, as 08:00 to 17:00, the system will try to schedule backwards from 17:00 instead of scheduling backwards from 23:59:59 (bucket finish). The search for a suitable slot on a resource ends at the beginning of the planning horizon. This is determined by the current time and the offset in the strategy profile. The beginning of the bucket is therefore ignored during backward scheduling. If the system is unable to find a sufficient gap on a finite resource between the beginning of the planning horizon and the end of the bucket, it cannot convert the SNP order using backward scheduling.
With the "Forward" strategy setting, the system transfers the start time of the first activity of an SNP order and it tries to create a PP/DS order from that time into the future. In this case, similar to backward scheduling, the capacity utilization with finite resources and the working times of the resource are taken into account. If the working times of the resource are defined as 08:00 to 17:00, the system will try to schedule a PP/DS order only after 08:00 towards the future (instead of 0:00:00 which is the start of bucket). The search for a suitable slot on a resource takes place up to any time in the future. The bucket end from SNP planning is ignored here.
If you have the planning direction "Backward with Reverse", the system creates the PP/DS order with forward scheduling if no suitable slot could be found using backward scheduling.
The planning direction "Forward with Reverse" is not useful for converting SNP planned orders. There is no point in time where forward scheduling would switch to backward scheduling.
Using a finite scheduling strategy (find slot, insert mode, squeeze in) during the conversion of SNP planned orders to PP/DS planned orders has the following disadvantages:
We therefore recommend that you use an infinite planning strategy to convert SNP planned orders to PP/DS planned orders. The system will then create all of the orders of a bucket at the same date. After the conversion, you can improve the planning result using, for example:
If SNP planning was carried out finitely with bucket resources and if not all planned orders can be planned in the bucket planned by SNP, the available capacity of the bucket resource may be too large. Check whether the available capacity for the bucket resource is too large.
When you make the general settings in the strategy profile, you must take the following aspects into account:
When you make the settings for dependent objects in the strategy profile, you must take the following aspects into account:
These settings apply to APO Release 3.0 and 3.1.
Splitting SNP Receipt Elements
======================================================
The conversion from SNP to PP/DS also entails a change in the planning semantics from the quantities per planning period that are planned in SNP to orders. The order sizes in PP/DS are determined by technical feasibility, among other things. In many cases, the order quantity required in PP/DS will not correspond to the production quantity of a planning period.
The option of splitting lot sizes during conversion was implemented in APO Release 3.1. The following options are available:
The smaller PP/DS orders that are generated in this way are a better basis for the requirement-synchronous production in a period.
Setting The SNP Planning Area
===================================================
Order categories are used to select the SNP orders for the PP/DS release. The order categories for the SNP orders are defined in a planning area. If a planning area is used during the conversion and this planning area does not contain any of the specified SNP order categories, the system does not select any SNP orders for the conversion.
During the order conversion, you can use the planning area to read the order categories globally from Customizing. Alternatively, you can use the planning area to select the order categories for a specific application from the initial screen of the transaction. The application-specific selection allows you to define several planning areas, which may contain different order categories. As a result, you can use different planning areas in a flexible way without making global changes in Customizing.
Setting The Package Size (APO Release 3.1)
=====================================
The packaging of the SNP orders controls system performance during the creation of PP/DS orders in the liveCache.
During this, due to the lot-size calculation, several PP/DS orders can be created simultaneously. In this case, we recommend that you reduce the package size because the number of PP/DS orders is greater than the package size of the SNP orders when an order is created; this may impair system performance during the conversion.
In large packages, conversion has a disadvantage if at least one order cannot be created during the PP/DS order creation. As a result, no SNP orders contained in the package are converted. However, the number of unconverted SNP orders and information about the quantity, availability date/time, and the location products affected are recorded in the planning log. It distinguishes between incorrect SNP orders and SNP orders that can be subsequently converted in the second run.
We recommend that you keep the package size as small as possible to ensure that the system converts as many orders as possible. However, this has a negative impact on system performance.
Alternatively, you can start the conversion twice: Once with a bundle of SNP orders in large packages (200, for example). The second time, you can start the same selection with smaller packages (package size = 1 SNP order, for example). In this way, at least those SNP orders for which no errors occurred during the PP/DS order creation are converted.
In addition, you have the option of restricting the selection to only those products that can be converted subsequently. In this way, packages can retain their original package size.
Why Do We Have To Perform An MRP Planning Run?
====================================================
You cannot use a procurement planning heuristic to plan a product that is procured using the converted SNP receipt elements. Typically, old receipt elements that no longer correspond to the current planning situation are deleted and replaced with new receipt elements for this type of procurement planning heuristic. In this case, the selection of sources of supply (source selection) for the old receipt element is lost. From a cost point of view, however, the selection of sources of supply is one of the most important advantages of using the SNP optimizer. If you want to retain this selection of sources of supply, you cannot execute procurement planning heuristics in PP/DS.
The planning procedure also determines whether the existing planned orders are exploded again when you change the plan (PPM or PDS). It is very useful to explode PP/DS planned orders again when the plans are changed. This is set in standard Customizing of the "Manual planning" planning procedure). Only one planning file entry is created for the new explosion when changes are made to plans. The actual new explosion occurs in the MRP planning run. An MRP planning run is therefore also required in this scenario.
Disadvantages Of Conversion
=======================
The disadvantages of converting from SNP to PP/DS are as follows:
The PP/DS Receipt Elements Are Not Adjusted To Changes In Requirement
==============================================================
In this integration scenario, all new receipt elements are exclusively created by SNP. In this way, you can ensure that the SNP source of supply determination is always used. On the other hand, only SNP planning performs the downwards adjustment of receipt quantities when requirements are reduced. However, since PP/DS receipt elements are fixed for SNP planning, this is not always possible in the suitable bucket. If a requirement is reduced within the PP/DS horizon (and if all of the SNP receipt elements within the PP/DS horizon have already been converted to PP/DS receipt elements), SNP planning is unable to adjust the receipt elements that cover the requirement. Instead, the system has to reduce SNP receipt elements in a later period so that the total number of receipt elements and requirements is correct again. The PP/DS receipt elements then cover requirements outside the PP/DS horizon.
There Is No Make-To-Order Production
===========================
Make-to-order production is not possible. SNP generates all receipt elements and only converts them to PP/DS receipt elements at a later stage. SNP planning does not support the make-to-order production.
Lot-Size Calculation In PP/DS
==========================
If the PP/DS receipt elements are created using conversion, the system cannot perform the PP/DS lot-size calculation. The lot sizes of PP/DS receipt elements are not related to the requirements in the PP/DS horizon. Lot-for-lot order quantity and periodic lot sizes are not supported.
Advantages
===========
Lot-Size Intervals From The PPM Are Used
===============================================
A common problem, particularly in process industries, is that alternative resources require different lot sizes in production. For example, a specific product can be produced in a reactor that can hold 1,000 liters or in a reactor that can hold 500 liters. Both alternative resources have alternative plans (PPMs) with different lot-size intervals. These alternative resources cannot be planned in the PP/DS procurement planning heuristic delivered by SAP or in the SNP heuristic. The reason for this is:
The heuristics execute the planning subfunctions in a specific sequence. During this, the system always determines the lot sizes first. Afterwards, the system carries out a selection of sources of supply. During this, the previously determined lot sizes have a restrictive effect on the selection of sources of supply. If, in the above example, the lot-size calculation determines a lot size of 1,000 liters, the production can only take place on the first reactor. If, on the other hand, the lot-size calculation determines a lot size of 500 liters, production can only take place on the second reactor.
The SNP optimizer can correctly plan alternative sources of supply with different lot-size intervals. In the above example, if the requirement is 1,000 liters, the SNP optimizer either creates an order for 1,000 liters with the first plan or two orders with the second plan, depending on the costs and the utilization of the resources. The result of the SNP optimizer can be transferred by converting SNP orders to PP/DS orders.
Advance Production And Deliberate Delays
================================================
One result of SNP planning may be a requirement, which you want to cover several planning periods earlier using an advance production. In particular, this is often the case if the requirements undergo seasonal fluctuations. By considering storage costs and the costs for alternative sources of supply, the SNP optimizer can determine an optimal stock policy for the most important products.
SNP planning may decide to use a scarce resource to manufacture a product with a high added value first, and to manufacture another product competing for the same resource later.
If a separate procurement planning heuristic is executed in PP/DS planning, these SNP planning decisions may be destroyed.
The PP/DS procurement planning heuristics work on the assumption that requirements are covered as soon as possible. These heuristics do not recognize that a receipt element is intended to cover a requirement outside a time interval determined by the lot-sizing procedure. If the receipt element is within the PP/DS horizon but the requirement is outside the PP/DS horizon and outside the time interval determined by the lot-sizing procedure, the PP/DS procurement planning heuristic deletes the old receipt element and does not replace it with a new receipt element. If the peak of the season is reached, even PP/DS planning must recognize that the requirements cannot be covered immediately.
If the conversion from SNP to PP/DS is used, the dates/times determined by SNP planning are retained. The problems regarding the procurement planning heuristic do not occur.
SNP and PP/DS in different planning versions
Planning Process
==============
Procedure
==========
You copy stocks, fixed PP/DS planned orders and fixed purchase requisitions, production orders, and purchase orders (that is, all objects that can no longer be changed in PP/DS planning) from the active planning version to the SNP planning version. You use transaction /SAPAPO/VERCOP to copy the version.
You execute SNP planning in the usual way in a planning version not equal to "000".
Once you are happy with the SNP planning result, you transfer the production plan to Demand Planning using transaction /SAPAPO/LCOUT.
Using transaction /SAPAPO/MC90, the planned independent requirement that is required is generated from the Demand Planning key figure that is determined in this way.
You can use either transaction /SAPAPO/LCOUT or transaction /SAPAPO/MC90 to change the planning version. You must copy "000" to the target planning version for one of the two copy operations.
In planning version "000", you execute PP/DS planning with the usual tools, such as background scheduling using transaction /SAPAPO/CDPSB0.
Planning Version Settings
=============================
In the planning version (transaction /SAPAPO/MVM), you can make settings that prevent safety stocks from being taken into account in PP/DS planning. The safety stocks were already considered during planning in SNP. Otherwise, the safety stocks are taken into account twice, once in SNP and once in PP/DS. The result of this planning is transferred to PP/DS. In planning version "000", you must therefore set the PP/DS indicator for taking the safety stock into account to its default value.
In the SNP planning version, you can deactivate the creation of planning file entries for PP/DS. This indicator has no effect unless a PP/DS planning run is started in this planning version or an MRP heuristic is carried out in the planning version. However, system performance is improved if no unnecessary planning file entries are created. We therefore recommend that you do not set the indicator for "PP/DS: Change planning active" in the SNP planning version.
Conversely, you can deactivate the creation of planning file entries for SNP in the active planning version "000". In the planning version "000", do not set the indicator for "SNP: Change planning active".
In planning version "000", PP/DS change planning is active.
In the SNP planning version, SNP change planning is active.
Requirement Strategy Settings In The Product Master
==================================================
A PP/DS procurement planning heuristic initially covers the planned independent requirements that were generated from SNP planning. These planned independent requirements can be consumed against sales orders at a later stage. Requirement strategy 20 and the consumption period must be set in the product master for this purpose.
Very often, the production plants will have to not only cover the sales orders, but also stock transfers to other plants or dependent requirements arising from further processing of the product. In this case, we require what is called "subassembly planning".
Set the subassembly planning as follows:
You require a category group containing the categories of all requirements against which planned independent requirements are to be offset. You create the category group using transaction /SAPAPO/SNPCG. Depending on what you require, the category group contains categories for sales orders, dependent requirements, and stock transfer requirements.
Afterwards, create a new requirement strategy in Customizing (transaction SPRO, menu path: SAP APO -> Master Data -> Product Master -> Specify Requirements Strategies). If planned independent requirements have the category "FA" and the assignment mode "1", they are offset against all categories from the new category group.
Set the indicator for subassembly planning in the product master and set the new requirement strategy.
Version Copy Settings
===============================
The version copy is executed using transaction /SAPAPO/VERCOP. Copy the master data and the transaction data and select the checkbox for the order data. You must at least specify the categories for stocks, production orders, purchase orders, firmed planned orders, and fixed purchase requisitions.
All receipt elements that are fixed for PP/DS planning must be copied to the planning version of SNP planning for the following reason:
If the receipt elements are not copied, SNP planning does not know about these receipt elements. In this case, SNP planning creates new SNP receipt elements to cover the requirements for the product. Very often, these new SNP receipt elements have another source of supply and will utilize other resources. SNP planning and PP/DS planning start to deviate from each other.
The SNP optimizer can plan stock transfers and the production in a way that ensures optimum use of existing fixed receipt elements. Of course, this is particularly useful when the requirements and the fixed receipt elements are in different locations. The fixed receipt elements must also be known to SNP planning in this case.
Stock Transfers
============
In the scenarios described above, the sales orders are returned directly from the production plants. This is the simple scenario. The ATP check selects the production plant.
If the sales orders are delivered from distribution centers and if there are possibly several alternative production plants for supplying a distribution center, stock transfer purchase requisitions must be created for supplying the distribution center. You have the following options for this:
Advantages Of Planning In Separate Planning Versions
================================================
Executing SNP planning and PP/DS planning in different planning versions has the following advantages:
Stability Of Planning
======================
SNP planning is frequently used for medium-term to long-term time frames. With these time frames, it does not always make sense to include all current changes to the actual data immediately in SNP planning:
If you execute SNP planning in your own planning version, you can select the time of the version copy and thus specify exactly which data is included in SNP planning and how often the data is updated.
Checked SNP Plans Are Released To PP/DS
=====================================
If you execute SNP planning and PP/DS planning in the same planning version, all changes in SNP planning are immediately taken into account in PP/DS planning. If, for example, an SNP planned order generates a dependent requirement for a component within the PP/DS horizon, a PP/DS planning run will try to cover this dependent requirement. However, in many cases this measure may be premature because the SNP planned order will be changed several times.
If SNP planning and PP/DS planning are executed in different planning versions, you have the option to release only checked, reconciled, or approved SNP plans to PP/DS planning.
SNP Planning And PP/DS Planning Are Performed At Their Own Frequency
==========================================================
As mentioned above, SNP planning is a period-based planning function and the intervals used to execute SNP planning are often based on these planning periods. PP/DS planning, in contrast, operates so that it is accurate to the second and should therefore be executed far more frequently.
As long as SNP planning and PP/DS planning are carried out in different planning versions, each planning can operate at its own frequency.
Distribution Across System Boundaries
=============================
The BAPI "PlanningBookAPS" is one of the building blocks which allows SNP planning and PP/DS planning to be carried out on different APO systems. For this, the time series from Demand Planning are exchanged between the systems.
All other alternatives discussed here execute SNP planning and PP/DS planning in the same planning version. Distributing the functions across different computers is not possible in this case as a matter of principle.
Stock Build-Up Is Enabled In SNP
=============================
If SNP planning wants to execute a stock build-up to cover a seasonal requirement that occurs at a later stage, this stock build-up is transferred to PP/DS planning. This occurs on the condition that the SNP receipt elements are transferred to Demand Planning using transaction /SAPAPO/LCOUT. Only SNP receipt elements show the stock build-up. Another condition is the creation of planned independent requirements with final assembly using transaction /SAPAPO/MC90. These are the only requirements that allow advance production.
Adjusting The Production To The Requirements Is Possible
===========================================
Planned independent requirements are generated from the result of SNP planning. These planned independent requirements are consumed with sales orders, and dependent requirements and stock transfer requirements for the same product, if applicable. The planned independent requirement is reduced and the sales order, the stock transfer requirement, or the dependent requirement is taken into account for the requested delivery date or the requirement date/time. This changes how the requirements are chronologically distributed. A new PP/DS planning run takes account of this change in distribution.
All sales orders are taken into account in PP/DS planning even if the total of sales orders exceeds the quantity planned using planned independent requirements. In this case, an adjustment in relation to the confirmed requirements also takes place in PP/DS planning.
However, automatic adjustment (reduction) of the planned production does not occur where the quantity planned using planned independent requirements exceeds the total of sales orders and any stock transfer requirements and dependent requirements. Stock build-up would not be possible either if the planned production was adapted to the confirmed requirements in this case.
If you do not want to use the stock build-up, you have two other options for handling a situation in which the quantity of planned independent requirements exceeds the total of sales orders:
Make-To-Order Production Is Possible
=============================
The planned independent requirements created using SNP planning can also be consumed with sales orders for make-to-order production. For this purpose, you must use a requirement strategy with assignment mode "2" in the product master. Usually, requirement strategy 30 (planning without final assembly) is used. If you want to combine make-to-order production with the option of stock build-up, you need a planned independent requirement for the planning with final assembly. For this purpose, create a separate requirement strategy with planning segment initial and assignment mode #2'.
Disadvantages:
==========
Planning SNP and PP/DS in separate planning versions has the following drawbacks:
==================================================================
By defining alternative plans, you can model and plan alternative resources within a production plant in SNP. SNP planning generates planned orders with different sources of supply or plans. All these planned orders are aggregated to a single key figure in the Demand Planning. In this case, PP/DS planning no longer possesses any information about the resource selection in SNP. As a result, only the source selection at a higher level, that is, at production plant level, can be transferred to PP/DS planning.
PP/DS MRP with standard lot size heuristic
Converting SNP receipt elements to PP/DS receipt elements has some disadvantages:
Often, users try to avoid the disadvantages of converting SNP receipt elements to PP/DS receipt elements by carrying out both a SNP planning run and a PP/DS planning run (with a standard lot size heuristic, for example) in the same planning version. The standard lot size heuristic in PP/DS can handle make-to-order production it can adjust PP/DS receipt elements to changed requirements. In this case, why not simply combine the two planning procedures? The new objectives are:
Algorithm
============
The procurement planning heuristics in PP/DS, such as the standard lot size heuristic, carries out the following steps consecutively for each product:
Settings
==============
The procedure requires the following settings:
Net Requirements Calculation Using FIFO Strategy
=========================================
If the default settings are used for the net requirements calculation in PP/DS, the net requirements calculation first uses fixed receipt elements to cover later requirements. This also occurs if the requirement is outside the PP/DS horizon and we would expect it to be covered by the SNP planning function. If the fixed receipt is used for later requirements, an earlier requirement may remain uncovered. The PP/DS heuristic creates a new receipt element for this requirement. If the requirement was already covered by an SNP receipt element outside the PP/DS horizon, this SNP receipt element becomes a surplus (until the next SNP planning).
To solve this problem, you must ensure that the delayed fixed receipt covers the preceding requirement. You have the following options:
Why Must Delays Be Allowed In SNP Planning?
============================================================
If a FIFO strategy is set for the net requirements calculation and if delays in SNP are not permitted, the effect is as follows:
PP/DS planning creates receipt elements for the requirements within the PP/DS horizon. However, some of these elements are delayed. The delayed receipt elements are not used by the SNP net requirements calculation to cover the earlier requirements. The delayed receipt elements are therefore available for requirements outside the PP/DS horizon. These requirements are neither covered by PP/DS planning nor by SNP planning.
You set the maximum delay for the SNP optimizer in the product master on screen SNP1.
The net requirements calculation in PP/DS and SNP should return the same result if PP/DS and SNP are to cover the same requirements.
Why Perform The Net Requirements Calculation On Requested Quantities?
============================================
In SNP planning, planning is usually executed for requested quantities. In the PP/DS standard lot size heuristic, you can choose between planning with requested or planning with confirmed quantities in the sales order in APO 3.0 and 3.1. The following problems may occur if you configure that PP/DS planning is carried out on the basis of the confirmed quantities:
Why Does The PP/DS Horizon Have To Be Initial?
============================================
The net requirements calculation carried out in SNP is different to the calculation performed in PP/DS. In SNP, all requirements for a planning period (bucket) are covered by the receipt elements in the same planning period. To cover new requirements within a planning period, SNP planning often creates a receipt element in the middle of or at the end of the planning period. This always occurs in SNP for daily periods and depending on the period factor for other planning periods. In contrast, receipt elements in PP/DS must be available before the requirement for it to be covered.
This causes the following problem: SNP planning created an SNP receipt within or at the end of the planning period to cover a requirement at the start of the planning period. From the PP/DS point of view, the requirement appears to occur before the receipt element. Therefore, the requirement cannot be covered by the existing SNP receipt element.
If both the SNP receipt element and the requirement are within the PP/DS horizon, PP/DS planning simply deletes the SNP receipt element and creates a new PP/DS receipt element. The receipt elements total then corresponds again to the requirements total. There is no sign of the problem.
However, if the requirement is within the PP/DS horizon and the SNP receipt element is outside the PP/DS horizon, PP/DS planning must not delete the SNP receipt element. Unnecessary SNP receipt elements are present until the next SNP planning.
This is particularly irritating if these SNP receipt elements generate dependent requirements. The system can no longer tell whether dependent requirements have originated from SNP or PP/DS. In this case, it is likely that too many component requirements will be procured.
To avoid this problem, let the PP/DS horizon always move on by one planning period. The PP/DS horizon moves on by one planning period each time if the following conditions are met:
What Is To Be Considered When Using Periodic Lots In The PP/DS?
=====================================================
For periodic lots, you expect the system to cover all requirements within a period using a single receipt element. If part of the period falls outside the PP/DS horizon, the system also expects all requirements (inside or outside the PP/DS horizon) to be covered by a single PP/DS receipt element. If the system had to increase the PP/DS planned order during the period by the quantities of the additional requirements trickling into the PP/DS horizon, all planning actions already carried out with this PP/DS receipt element would be invalidated. In this case, the user would have to repeat a scheduling run, rescheduling, campaign assignment, ATP check, and so on.
If the requirements were in different SNP planning periods, the part of the PP/DS lot size period outside the PP/DS horizon would still be covered by user-defined SNP receipt elements. Accordingly, the shortage for the PP/DS would be smaller. PP/DS planning could cover only part of the requirements in the period.
Therefore, the following conditions are required: Firstly, the PP/DS horizon must move on by SNP planning periods, and secondly, the periods for PP/DS lot-size calculation must not be greater than the planning periods.
The period boundaries of the SNP planning periods must be the same as the limits of the periods used in the PP/DS lot-size calculation. If monthly periods are used in SNP, the lot-size calculation can create daily lots, 10-day lots, or monthly lots in PP/DS, but it cannot create weekly lots because Mondays usually do not fall on the first day of a month. If weekly periods are used in SNP,
daily or weekly lots can be used in PP/DS.
Why Must SNP Planning Be Executed Before The MRP Planning Run?
====================================================================
The PP/DS horizon is relevant only for make-to-stock production. For make-to-order production, the entire time axis is within the PP/DS horizon. A make-to-order sales order outside the PP/DS horizon reduces the planning quantity and acts as a separate requirement element for the MRP planning run. MRP planning covers this requirement using a new planned order. If no SNP planning run is executed previously, the SNP planned order still contains its original quantity for the make-to-stock production. The quantity of the SNP planned order is too large. The combined totals of SNP planning and PP/DS planning constitute an overproduction. Too many components are procured and too many resources are reserved.
Disadvantages
==========
The SNP Selection Of Sources Of Supply Is Lost
======================================
During this procedure, the SNP orders are deleted by the MRP heuristic in the PP/DS horizon. Instead, the MRP heuristic creates PP/DS receipt elements to cover the requirements within the PP/DS horizon. The PP/DS receipt elements are in no way related to the original SNP orders. The source selection of the SNP order cannot be transferred to the PP/DS order. The PP/DS heuristic carries out its own source selection which, of course, returns a result that differs from the SNP planning result.
This is only a problem if alternative sources of supply actually exist for the product. It is not a limitation if single sourcing is used. However, it is a serious limitation if alternative sources of supply are available. After all, SNP planning is carried out specifically to optimize the selection of sources of supply. If the results from this planning cannot be copied to PP/DS planning, the entire SNP planning run serves no purpose.
You could try to avoid this drawback by converting SNP planned orders to PP/DS planned orders between the SNP planning run and the PP/DS planning. However, this will not stop PP/DS planning from performing a new source selection. PP/DS planning always carries out a new source selection if a quantity or date/time for the converted planned order does not match the requirement. The planning process is complicated further by the additional conversion.
Advance Production (Early Build)
====================================
Of course, SNP planning can meet a future requirement with an earlier procurement. This option is particularly useful for seasonal fluctuations in requirements and limited capacities. Depending on the storage and procurement costs, the SNP optimizer can find a solution which allows the requirements from a future period to be covered using a production in an earlier period. The procurement planning heuristics provided by SAP in PP/DS, on the other hand, can support only requirement-synchronous procurement. If the requirement is outside the PP/DS horizon but SNP has scheduled a receipt within the PP/DS horizon, the standard lot size heuristic would delete the SNP receipt from the PP/DS horizon without replacing it.
To solve the problem, some PP/DS heuristics have an indicator for taking into account shortages outside the production horizon. If this indicator is selected, the PP/DS heuristic adds up all shortages outside the PP/DS horizon and within the period specified in the heuristic. Due to the limited resources available, SNP cannot cover these shortages itself and expects these product requirements to be covered by receipt elements in the PP/DS horizon.
If you want to retain a stock build-up planned by SNP, you must ensure the following aspects:
If the indicator for taking account of shortages outside the production horizon is set, all shortages in the specified period are added up and moved to the end of the PP/DS horizon. There, they are treated as ONE requirement. If there is an exact lot size, the entire stock build-up is carried out by a single receipt element. This receipt element may be very large and therefore difficult to deal with or difficult to plan. Check whether a maximum lot size can be used to cover the requirement using several receipt elements.
The Planning Process Is Complicated
============================
As described above, an SNP planning run must be executed before every PP/DS planning run. This is not how an ideal planning run is expected to work.
SNP planning is a long-term and period-based planning system. The planning periods in SNP are often weeks or months. From an SNP point of view, there is no reason to execute SNP planning more often than once per planning period. This is unless the previous period was so poorly planned that the actual data differs significantly from the planned data and this actual data is to be taken into account in SNP planning.
System administration is also complicated by the interdependencies between the planning runs. Ideally, the sequence of planning runs should be variable.
In a system with 7*24 hour availability, it is even necessary for each planning run to store a consistent overall plan when it is completed because the planning results may be read at any time. This requirement cannot be met by integrating SNP and PP/DS with the approach described.
Lack Of Transparency
=====================
During the conversion from SNP to PP/DS, conflicting objectives may arise. The objectives of SNP and PP/DS will contradict each other if SNP tries to avoid seasonal capacity overloads using an advance production and at the same time, PP/DS only releases production if the sales order is already available or PP/DS executes a make-to-order production or PP/DS always adapts the planning to sales orders.
If SNP planning and PP/DS planning are executed in separate planning versions, the planning results of both plans are always available and comprehensible (as far as the optimizer allows). If there are conflicting objectives, the SNP planner and the PP/DS planner can use their respective planning results for the required adjustments.
If SNP planning and PP/DS planning are carried out in a single planning version, there is a risk that the SNP planning result is destroyed by PP/DS planning (at least within the PP/DS horizon). As a result, the results of SNP planning are no longer comprehensible and they can no longer be used for a reconciliation between the planning levels that may be required.
Functions that behave differently in SNP and PP/DS
Safety Days' Supplies
======================
SNP and PP/DS treat safety days' supplies differently. In SNP, the following logic applies: In period n, cover the requirements of periods n to n+safety days' supplies. In PP/DS, the following logic applies: Cover the requirements from period n in period n-safety days' supply. If the safety days' supply is static, these two logics differ only for the period from the current point of time until the end of the safety days' supply. SNP creates only one receipt element for this period, while PP/DS may create several receipt elements (provided that there are several requirements in this period and lot size grouping does not take place). The differences are greater for time-dependent safety days' supplies. SNP uses the following logic: In period n, cover the requirements of periods n to n+safety stock(s)". SNP uses the safety days' supply at the time of the receipt element. PP/DS uses the following logic: Cover the requirements from period n in the period n-safety days' supply (or safety days' supplies). PP/DS uses the safety days' supply at the time of the requirement element.
Solution
*
The following questions arise in connection with the integration of Supply Network Planning (SNP) and Production Planning and Detailed Scheduling (PP/DS):
- What are the differences between SNP plans and PP/DS plans?
- What are mixed resources?
- How do I set up mixed resources?
- I work with periodic lots in the PP/DS heuristic. If part of a period is outside the PP/DS horizon, the PP/DS order nevertheless covers the requirements in the second half of the period. This means that requirements outside the PP/DS horizon are covered by PP/DS. Why? Does this not affect the separation of SNP and PP/DS?
- What is the function of the heuristic switch for taking into account shortages outside the production horizon?
- SNP plans a stock build-up. This stock build-up is destroyed by PP/DS. How can I prevent this?
- Is there a heuristic that considers the requirements only up to the horizon end in the planning?
- What is the role of mixed resources?
- I use mixed resources. After the system converts an SNP planned order to a PP/DS planned order, the capacity requirements in the SNP capacity view differ from the capacity requirements before the conversion. Why?
- What is modeled using the lot-size intervals in the SNP production process model (PPM) and in the PP/DS PPM?
- What do I need to take into account regarding lot sizes when converting from SNP to PP/DS?
- Which planning area is relevant for the SNP->PP/DS order conversion?
- What strategy profile is to be used for the SNP->PP/DS order conversion?
- Packaging SNP orders during the SNP order conversion
SNP-PP/DS integration, documentation, FAQ, production horizon, PP/DS horizon, SNP->PP/DS
Reason and Prerequisites
Comparing SNP with PP/DS: SNP
The Role Of SNP
=================
SNP planning makes the decisions on tactical planning and source of supply determination. The strengths of SNP planning are: The selection of the source of supply taking into account the costs, and the determination of the approximate production date taking into account both the procurement costs and the storage costs. The result of the SNP planning is the answer to "What is produced, where and when?". The answer to "when" cannot be more precise than a planning period, and it does not take the sequence-dependent setup activity into account.
The SNP Optimizer
===================
The SNP optimizer performs cost-based optimization. The SNP optimizer creates a production plan in a way so that an objective function is as close to its minimum value as possible. The objective function is the weighted total of the following costs:
- Production costs, procurement costs, storage costs, and transportation costs
- Penalty costs for non-coverage or delayed coverage of the requirement or the safety stock
- Costs for increasing the capacity (with regard to the production, the storage, the shipment, and so on)
The SNP optimizer is therefore able to make the following decisions in particular:
- A product is subject to seasonal fluctuations. Is it cheaper to build up a warehouse stock in low season (storage costs) or to use an expensive source (in-house production or external procurement)?
- You can either procure a product externally or produce it in-house. In the current requirement situation, is it cheaper to procure a product externally (in this case, the resource is available for the production of another product) or to produce it in-house?
- A product is in stock in one plant, but it is required in another plant. Is it more favorable to transfer the product (as a result, a future requirement may have to be covered differently in this plant) or to produce it again in-house?
- A resource can produce a quantity A of products. Different costs are incurred when these products are produced. Another resource can produce a different quantity B of products. The quantities A and B have an intersection. On which resource are the products from the quantities A and B produced at the lowest cost?
The SNP optimizer determines the following:
- The production quantities, the procurement quantities, the stock transfer quantities for each product and period
- The selection of the resources and the plans for the production
- The selection of the plants, the warehouses, the suppliers, and the transportation lanes
The SNP optimizer works on the basis of periods. The sequence of orders within a planning period is not defined. This has the following consequences:
- The SNP optimizer can consider only a constant setup time. Sequence-dependent setup times or sequence-dependent setup costs are not supported.
- It can only provide a rough model for the material flow. In principle, a material flow occurs only at the period boundaries.
Setup In The SNP Optimization
===============================
SNP planning is period-based planning. SNP planning determines the production quantities for each period; it does not determine the sequence of production orders. Therefore, SNP planning cannot take into account the exact effort required for the setup.
Usually, setups in SNP optimization are only taken into account by a setup allowance. The attributable capacity of a resource available in SNP is reduced by the loss factor. This means that a part of the capacity is kept free for the setup. You can set the loss factor for mixed resources in the master data of the resource.
Using the modeling option for fixed resource consumptions in SNP, the SNP optimizer supports a simple lot size planning, which may also be performed across periods for APO Release 3.1. Lot size planning reduces setup costs by summarizing the orders for large lots. With cross-period lot size planning (APO Release 3.1), the setup statuses of the previous period are taken into account when a product is produced in the current period with the same plan. This lot size planning is used in industries where setup operations greatly influence the production costs. If setups play a major role, you should try to ensure that the setups are already taken into account in SNP. SNP then generates plans that represent a reliable template for planning in PP/DS.
Material Flow In SNP Optimization
=========================================
The period factor or bucket offset controls the modeling of the material flow in SNP. If the period factor is high, you can often produce two or more production levels in one bucket. The lead times on several production levels become shorter. However, the result may be too optimistic. If you wish to err on the side of caution, you must work with a period factor of zero, but this is at the expense of the lead time.
The period factor in the product master applies only to the SNP heuristic. The same function can be applied in SNP optimization using the bucket offset in the SNP optimization profile and in the PPMs and transportation lanes.
Model Size And Complexity
===========================
Due to the runtime and memory requirements of SNP optimization, we must also think about the model size and the model complexity. Creating an SNP production plan is an NP-completeness problem. IT theory has taught us that there is no known algorithm to guarantee finding an optimal solution for the problem in polynomial runtime. For more information on NP-completeness problems, we recommend that you read the following book by Michael R. Garey and David S. Johnson: "Computers and Intractability: A Guide to the Theory of NP-Completeness".
In the case of SNP optimization, a distinction must always be made between purely continuous models and models known as discrete models. If fixed lot sizes, minimum lots, or piecewise linear cost functions are to be taken into account, you will require a discrete model. In this case, the system must perform a mixed integral optimization.
The continuous models are primarily restricted because of the memory required. However, the required runtime of purely continuous models is linearly dependent on the model size and is generally non-critical as a result.
On the other hand, the solution of discrete models using a mixed integral optimization can be considerably more complicated. It is generally not possible to guarantee the global optimum under realistic CPU time targets. Instead, permitted and high-quality solutions must be found with acceptable runtimes. The runtime and memory requirement of SNP optimization depends on the number of the variables. The number of variables is therefore restricted. You require a variable for each production quantity or procurement quantity that you want to determine using SNP optimization. In other words, you require a variable for each location product for each planning period. The practical upper limit is approximately two (2) million continuous variables or 100,000 discreet variables.
The following is an example of a continuous model:
7,000 products * 5 locations * 52 weeks = 1,820,000.
This type of continuous model already belongs to the large optimization models. This means that we require 4GB RAM for this continuous model. If the problem is too large or too complex, it may be simplified as follows:
- We are planning in large periods rather than small periods (months instead of weeks).
- We consider fixed order quantities, minimum lot sizes, and so on only where necessary.
- Non-critical products and resources are not included in the planning.
Restricting the model size is a considerable incentive for hierarchical production planning. In SNP planning, you often have to work on aggregated data in order to reduce the number of variables. Nevertheless, you should determine detailed production plans at a later stage. The detailed production plans are then created using PP/DS.
Advantages Of SNP Optimization
=============================
- Optimizing procurement costs while taking into account alternative sources of supply
- Taking capacities into account
- Distributing the production over several periods (during seasonal fluctuations, for example) while taking storage costs into account
Disadvantages Of The SNP Optimizer
=============================
The SNP optimizer has the following restrictions:
- It does not have a sequence-dependent setup activity.
- Planning takes places in planning periods (buckets). The order sequence is not defined within a planning period.
- The number of variables is restricted. It often happens that optimization can only consider some products or it has to work with large periods (usually months).
- Make-to-order production is not supported.
- Configurable products are not supported.
- The SNP plan does not permit different component validities. This must be modeled using several SNP plans. For more information, see Note 513868.
- It can only provide a rough model for the material flow. This basically occurs only at the period boundaries.
The SNP optimizer is therefore particularly suited to medium to long-term planning. You generally have to use the SNP - PP/DS order conversion to convert the result of the SNP optimizer to PP/DS orders. One of the actions you can then perform in PP/DS planning is to determine the exact sequence for production orders.
The SNP Production Horizon
============================
SNP does not create any orders within the SNP production horizon. The SNP production horizon can therefore be used to divide the responsibilities for planning among Supply Network Planning (the order is outside the SNP production horizon) and Production Planning and Detailed Scheduling (the order is within the SNP production horizon).
SNP Plans
==========
An SNP plan is the basis for planning in-house production in SNP and is stored in APO as SNP PPM or SNP PDS. SNP planning is primarily designed to provide a plan outlining the resource and component requirements in advance, and it does not aim to provide an exact model of all technical options. SNP plans are therefore simpler than PP/DS plans. Mode linkage, cover, minimum and maximum intervals of relationships, and so on are not important in SNP planning and therefore cannot be maintained in the SNP PPM. Alternative modes must be modeled in SNP as alternative PPMs or alternative SNP PDSs. An SNP plan refers to planning in planning periods. The length of an activity cannot be less than a day. SNP permits "day" as the smallest planning period. You can therefore plan accurately to one day at the most. In contrast, PP/DS permits planning to the exact second.
Validity Of SNP Plans
==========================
Usually, the lot-size intervals of an SNP plan differ from the lot-size intervals of the corresponding PP/DS plan. Typically, the lot-size interval of the SNP plan should correspond to the maximum quantity that can be produced in a planning period, while the lot-size interval of the PP/DS plan should correspond to the maximum order size. If several orders can be produced in a planning period, the lot-size interval of the SNP plan is usually larger than the lot-size interval of the PP/DS plan. If production takes longer than an SNP planning period, the lot-size interval may be smaller in the SNP plan than in the corresponding PP/DS plan.
Comparing SNP with PP/DS: PP/DS
The Role Of PP/DS
==================
The strengths of PP/DS planning are its consideration of sequence-dependent setup activities and restrictions that apply to the generation of production orders that can be produced: complete bills of material (BOMs) and routings, inclusion of change statuses and configuration. It also guarantees feasibility with planning that is exact to the second, and so on.
In general, lot sizes cannot be optimized independently of the sequence of the production orders. Lot size optimization is therefore regarded as being a PP/DS task. However, since you quickly encounter calculation limits, PP/DS offers only limited help during lot size optimization.
The PP/DS Optimizer
====================
Up to an including SCM 5.1, the PP/DS optimizer cannot create any new orders, but it optimizes the date and time of production and resource assignment of operations with regard to the following criteria:
- Total lead time
- Setup times
- Setup costs
- Delay costs
- Mode costs
These criteria form part of the objective function. The objective function is the weighted total of the criteria mentioned above. Optimization determines a production plan in which the required result, for example, the minimum setup times or sequence optimization, is achieved as far as possible. For this, the system varies the start times and the resource assignments of the operations. The system then uses the set objective function to assess the production plans created in this way. The production plan that has the minimum value for the objective function is the result of the optimization.
Read Note 712066 for further and more recent information about the PP/DS optimizer and restrictions for the PP/DS optimizer.
The PP/DS Horizon
==================
PP/DS planning is carried out within the PP/DS horizon. PP/DS planning usually does not create orders outside the PP/DS horizon.
The following exceptions exist:
- You can manually create PP/DS orders outside the PP/DS horizon.
- You can use transaction /SAPAPO/SNP2PPDS to convert SNP orders to PP/DS orders. In this case, all SNP orders within a PP/DS horizon and an offset are selected.
- The PP/DS optimizer can delay PP/DS planned orders from the PP/DS horizon if insufficient capacities are available within the PP/DS horizon.
- In the case of finite scheduling, the scheduler in the liveCache can delay PP/DS planned orders from the PP/DS horizon if insufficient capacities are available within the PP/DS horizon.
In APO Release 3.0, the PP/DS horizon is identical to the production horizon. In APO Release 3.1, the PP/DS horizon and the SNP production horizon may differ. If the PP/DS horizon is initial, the SNP production horizon is used as the PP/DS horizon. In this case, there is no overlap between the two horizons. If the PP/DS horizon is shorter than the SNP production horizon, the PP/DS horizon is extended to the SNP production horizon. The time axis does not have any area that is not planned by either PP/DS or SNP. However, the PP/DS horizon can also be longer than the SNP production horizon. In this case, there is an area on the time axis that is planned jointly by SNP and PP/DS.
PP/DS Plans
============
A PP/DS plan provides the basis for planning in-house production in PP/DS. PP/DS plans are stored either as PP/DS PDSs or as PP/DS PPMs. In PP/DS, the production process is described using activities that are linked through relationships. Several logically related activities form an operation. In discrete manufacturing, an operation is generally composed of setup activities and processes. In process industries, on the other hand, operations are often more complex. An operation in the process industry can therefore consist of activities such as mixing, stirring, heating, cooling and cleaning. The activities of one operation must not be interrupted by the activities of another operation. The switch for continuous reservation of the resource is set in the PPM. This feature is called "Cover". In the PDS, the Cover feature for the activities in an operation is always set automatically.
The activities of a PP/DS plan can be carried out on alternative resources. These are defined as a mode in the plan. Each mode can have a different duration. If an activity is carried out on a certain alternative resource, this can mean that subsequent activities must also be carried out on compatible resources. This is known as mode linkage. The simplest case of mode linkage is where setups and processes have to be executed on the same resource.
You require both components and resources to execute an activity. The component consumption of each activity is also defined in the PP/DS plan.
In APO, you can use PP/DS PPMs, iPPE models, or PDSs generated from R/3, as PP/DS plans. The PP/DS PPM or a PDS generated from R/3 is either a combination of an R/3 BOM and an R/3 routing, or a combination of an R/3 BOM and an R/3 recipe.
Do We Require Modes In PP/DS?
============================
SNP planning does not know the mode concept from PP/DS. The integration of PP/DS plans with SNP plans results in additional work if alternative modes are used in PP/DS. The amount of work involved can be reduced by not using alternative modes in PP/DS. However, the disadvantages of not using alternative modes in PP/DS are as follows:
- The PP/DS optimizer can independently select the alternative mode that allows the best production date. If no alternative modes are used in PP/DS, the PP/DS optimizer is unable to carry out a resource selection.
- With forward scheduling, scheduling of planned orders in the liveCache selects (upon request) the mode that allows the earliest production date. With backward scheduling, scheduling selects (upon request) the mode that allows the latest production date.
- In the graphical planning table, you can use drag and drop to reschedule an operation from one mode to an alternative mode. All of the alternative modes of an operation are highlighted in color. If no alternative modes are used in PP/DS, you cannot select resources using drag and drop in the graphical planning table. Instead, you must navigate to the order processing for the selected operation and change the source of supply for the order there.
Validity Of PP/DS Plans
============================
Usually, the lot-size intervals of an SNP plan differ from the lot-size intervals of the corresponding PP/DS plan. Typically, the lot-size interval of the SNP plan should correspond to the maximum quantity that can be produced in a planning period, while the lot-size interval of the PP/DS plan should correspond to the maximum order size. The maximum quantity that can be produced per order is usually defined by physical constraints (for example, the boiler size). A PP/DS planned order that is outside the valid lot-size interval cannot be produced.
SNP and PP/DS: Shared view of the planning situation
SNP is used to determine an optimal sourcing for the planning. The plan created by SNP must be detailed at a later stage. The aspects of planning that were not considered in SNP must be taken into account.
For example:
- The sequence-dependent setup activities
- The resource selection
- The exact production time within the planning period and the resulting sequence of operations on the resource
- The addition of components and capacity requirements that were not planned in SNP; this is to keep the model easy to handle.
PP/DS is used for these. If you want to add details to the SNP production plan or execute it, you must transfer the SNP production plan to a PP/DS production plan.
If SNP planning and PP/DS planning are carried out in a shared planning version, this results in several interfaces between the two plans:
- SNP planning must regard the results of PP/DS planning as fixed receipt or requirement elements.
- SNP planning must take into account the capacity consumption of PP/DS orders on mixed resources. If required, SNP planning takes into account the setup statuses on single mixed resources that result from PP/DS orders.
- The SNP production horizon of a product may be shorter than the PP/DS horizon. In this case, this leads to a product time interval that can be planned by both SNP and PP/DS.
- Even though two products have disjunct SNP and PP/DS horizons, both products are produced on the same resource. If the PP/DS horizons for these two products differ, a time interval that is jointly planned by SNP and PP/DS is created on the resource.
- Different production levels potentially have different PP/DS horizons. If the offset of the PP/DS horizons does not correspond to the negative lead-time offset, a dependent requirement from SNP planning must be covered by a PP/DS receipt element or vice versa.
- A controlled transfer to the PP/DS planned orders must take place for the planned orders created by SNP planning.
Fixing PP/DS Planned Orders In SNP Planning
====================================================
PP/DS receipt elements can be displayed for SNP, but these elements are fixed. The stocks and PP/DS receipt elements are read and offset against the existing requirements as part of an SNP heuristic or the SNP optimization. During this, it is irrelevant whether the requirements lie inside or outside the production horizon. As a result, requirements outside the production horizon may also be covered by receipt elements within the production horizon. In this case, SNP must create new SNP receipt elements only for the remaining uncovered requirements. SNP cannot change PP/DS receipt elements. SNP handles PP/DS receipt elements in the same way as it handles stocks. SNP planning is therefore unable to adjust PP/DS planned orders to a changed requirement situation.
PP/DS planned orders are fixed for SNP planning because they are processed using functions that SNP planning is unable to understand; for example, exact scheduling or the explosion of PP/DS plans. Even if unnecessary PP/DS orders are outside the PP/DS horizon, SNP planning cannot delete these orders.
Pegging
=======
The system creates pegging relationships between the product receipts and the product requirements regardless of whether the product receipts or the requirements involve SNP orders or PP/DS orders. This solves the following problems:
- The PP/DS horizon for a component is longer than the PP/DS horizon for the superior assembly. This will result in a situation where an SNP planned order is created for the assembly while PP/DS receipt elements already exist for the components. An SNP planned order can cover its dependent requirements from PP/DS receipt elements.
- A fixed lot size or a minimum lot size is set for a product. The requirement within the PP/DS horizon is smaller than the fixed lot size. This requirement is covered by a PP/DS receipt element. However, this receipt element is not fully required within the PP/DS horizon. The system uses the surplus to cover requirements outside the PP/DS horizon.
- The PP/DS horizon for an end product is longer than the PP/DS horizon for a component. A PP/DS planned order is created for the end product. The dependent requirement for this planned order is covered by an SNP receipt element during the next SNP planning for the component.
Mixed Resources
===============
Mixed resources allow SNP and PP/DS to have a shared view of the resource schedule. The capacity commitment from PP/DS orders is also displayed for SNP on mixed resources. For this, the PP/DS capacity commitment is converted to a bucket resource reservation.
Single-mixed resources correspond to single activity resources in the detailed scheduling. Multimixed resources correspond to multi-activity resources in PP/DS planning. In Supply Network Planning, mixed resources behave in the same way as normal bucket resources.
Mixed resources can serve their purpose only if the capacity requirements for the PP/DS planned order are approximately the same as the capacity requirements for the SNP planned order.
For PP/DS planned orders, a capacity requirement on the bucket resource is calculated from the capacity requirement on the single resource. As a result, PP/DS capacity requirements are also displayed in SNP. Finite SNP planning can create new planned orders within the SNP horizon if sufficient capacity is still available for SNP despite the capacity commitment caused by PP/DS planned orders. Since PP/DS planned orders are fixed for SNP planning, it is sufficient to simply reduce the capacity available for SNP by the portion consumed by PP/DS planned orders.
As of APO Release 3.1, single-mixed resources can be used to model block capacities for block planning in characteristics-dependent planning (CDP). If a mixed resource is used for block planning, it can no longer be used in SNP.
Integration Master Data: Resources
How Do I Set A Mixed Resource?
=======================================
In APO, you cannot convert a single-activity resource to a single-mixed resource. You cannot convert a multi-activity resource to a multimixed resource either. In this case, you must delete the old resource and create a new resource.
If the resources are transferred from the R/3 system, the resource type must be changed in the inbound interface of the APO system. (For more information, see Note 329733).
If the user exit for resources is used to create mixed resources from the R/3 system, the user exits for the objects that use the resources (especially PPM) must be adjusted. (For more information, see Note 321474).
Problem: Different Capacity Requirements In SNP And PP/DS
=======================================================
The bucket requirements of a mixed resource are calculated in the PP/DS planned order only so that SNP planning obtains an accurate picture about the reservation of the resource from the SNP view. SNP planning cannot plan the resource correctly if the capacity requirements differ.
Cause
=======
The system explodes the plan again when an SNP planned order is converted to a PP/DS planned order. During this, the capacity consumptions are determined again. If the bucket consumption in the PP/DS plan differs from the bucket consumption in the SNP plan, the capacity consumption of the orders generated from the plans also differ.
Solution
======
Ensure that the bucket consumption in the PP/DS plan is identical to the bucket consumption in the SNP plan. You will find the bucket consumptions in the PP/DS PPM and SNP PPM as follows: There is a navigation tree in the upper left part of the PPM maintenance screen. Open the operation and open the activity. Then open the mode and double-click the resource. If you use the PDS, you can use transaction /SAPAPO/CURTO_SIMU to display the bucket consumption.
In addition, the bucket consumptions in the PP/DS plan should correspond to the capacity requirements in PP/DS.
Example 1
==========
The available bucket capacity for our resource can be defined as follows: Capacity=1,000 pieces per week. The resource is a single-activity resource that works 40 hours per week. An order of 100 pieces requires four hours in PP/DS and reserves 100 pieces of the available bucket capacity. As a result, the bucket consumption is 100 pieces. You define the variable duration of four hours/100 pieces in the mode of the PPM. You define the variable bucket consumption in the resource chart of the PPM.
Example 2
==========
The comparison of SNP capacity consumptions and PP/DS capacity consumptions becomes especially intuitive if the available bucket capacity (and therefore, the bucket consumption) is defined in a time unit. The available bucket capacity can be defined as 40 hours per week. The resource is a single-activity resource that works 40 hours per week. An order of 100 pieces requires four hours in PP/DS and reserves four hours of the available bucket capacity. In this case, the bucket consumption is four hours. You define the variable duration of four hours/100 pieces in the mode of the PPM. You define the variable bucket consumption of four hours in the resource chart of the PPM. This seems to be an unnecessary duplicate entry. However, as example 1 shows, this is not the case because the dimension of the bucket consumption does not have to be a time unit.
Connection Between The Duration And Capacity Consumption
======================================================
As the above example shows, the durations in the mode and the bucket consumption must be consistently defined in the PP/DS plan. If this is not the case, incorrect bucket consumptions are calculated for PP/DS planned orders. In the SNP plan, there is no connection between the duration and the bucket consumption. The reason for this is the different scheduling in SNP and PP/DS. The duration in the mode of a PP/DS plan basically describes the pure production time. The queue times between the activities result from the resource availability or the relationships. On the other hand, the lead time including the queue times is contained in the mode of an SNP plan. As a result, there is no direct connection between the duration and the bucket requirement in SNP.
Fixed Capacity Consumptions
=========================
Fixed capacity consumptions are usually used to roughly model setup activities. Setup activities are required between orders that produce different products. SNP does not perform order-specific planning. Instead, the SNP plan acts as a form of data storage. SNP actually plans quantities for each time interval (bucket). Therefore, fixed capacity consumptions must be dealt with carefully. This applies in particular as of APO Release 3.1. As of APO Release 3.1, you can split the quantities planned by SNP during the conversion from SNP to PP/DS (according to the fixed or maximum lot size in the product master or the lot-size intervals in PPM). The fixed bucket requirement in PP/DS multiplies as a result of these splits. As a result, the differences between the SNP capacity consumption and PP/DS capacity consumption increase.
Available Capacity In SNP And PP/DS
======================================
If you have mixed resources, you can calculate the available bucket capacity from the continuous available capacity. However, you must bear in mind that part of the capacity in continuous PP/DS planning is required for the setup activity. As a result, the bucket capacity is generally a little smaller than the continuous capacity. The loss factor in the resource maintenance is available for this.
The loss factor must first be defined at random. The bucket capacity determined in this way therefore does not correspond exactly to the continuous capacity of the mixed resource. As a result, it is not guaranteed that a finite SNP plan created using the SNP optimizer, for example, can also be converted to a finite PP/DS plan.
You can check the accuracy of the bucket capacities only by analyzing the results of PP/DS planning and comparing them with SNP planning. If the PP/DS planned orders generate overloads on the continuous capacities (and these did not exist in SNP planning), the setup sequence is either poor or the bucket capacity is too high. If there is sufficient unused capacity in the PP/DS (which is not visible in SNP), we can assume that the bucket capacity is too low.
Even if this type of capacity control is considered to be important if the overall process is to work over a long period of time, we advise against having excessive accuracy requirements. With sequence-dependent setup activities, the capacity requirements on the continuous resource constantly change every time the sequence of production orders changes. The bucket capacities should not be changed every time for SNP. Capacity overloads and underloads of 10% are certainly tolerable.
Master data integration: PPM
You can either create SNP PPMs manually, or you can create them from PP/DS PPMs using a generation report. The integration of SNP planning and PP/DS planning requires the following:
- SNP master data and PP/DS master data describe the same process (of course while considering the different detailing requirements).
- It is possible to establish a relationship between the SNP master data and the PP/DS master data. This type of relationship can be used during the conversion of SNP planning to PP/DS planning so that PP/DS planning uses the same sources of supply and resources that SNP planning used.
SNP PPM and the corresponding PP/DS PPM can only claim to describe the same process if the following conditions are met:
- The lot-size intervals of SNP PPMs and PP/DS PPMs are defined differently. The lot-size interval in the SNP PPM describes the quantity that can be produced in a planning period. The lot-size interval in the PP/DS PPM describes the lot-size interval permitted for a single production lot. These two lot-size intervals must be converted correctly.
- The temporal validity intervals of the SNP PPM and PP/DS PPM are identical.
- The component requirement quantities are identical.
- The operations to which the component requirements in the SNP PPM are assigned correspond to the operations in the PP/DS PPM with the same component requirements. Example: A PP/DS PPM operation lasts several SNP planning periods. Several operations are created for the SNP PPM. The component requirement in the SNP PPM must be assigned to the first of these operations.
- There is an SNP PPM for each of the most important modes used in PP/DS.
- The use of mixed resources is a prerequisite for the integrated SNP PP/DS planning. The bucket consumption in SNP must correspond to the PP/DS capacity consumption.
- The mode duration in the SNP PPM must be calculated correctly.
The best way of meeting these requirements is to use the SNP PPM generation from PP/DS PPMs. Otherwise, you must ensure that both PPMs describe the same processes from an organizational point of view.
Generated SNP PPMs
===================
SNP PPMs can be generated from PP/DS PPMs. During this, the bucket consumption of the SNP PPM is determined from the mode durations of the PP/DS PPM. We can therefore assume that the available bucket capacity of the resource has the "time" dimension.
In Release 3.0, the variable SNP bucket consumption consists of the variable bucket consumption and the fixed bucket consumption of the PP/DS PPM. When determining the variable SNP bucket consumption, the variable consumptions of the output product and the maximum lot size of the PP/DS PPM are also taken into account. The fixed SNP bucket consumption is not supported in Release 3.0. The fixed duration in the SNP PPM is determined from the duration of an SNP planned order for a bucket size. However, a user can use a user exit to maintain the bucket consumptions and the duration in SNP PPM. In this case, the user is responsible for the consistent maintenance of the bucket consumption within the PP/DS PPM.
Generating The SNP PPM
=====================================
Refer to Notes 516260 and 323884.
Determining The Capacity Requirement
=================================
In addition to defining the duration, you must also define the bucket consumption for a mode when maintaining a PP/DS PPM with a mixed resource. This bucket consumption is transferred to the SNP PPM as a capacity consumption. The bucket consumption does not have to be defined in the "time" dimension. However, the conversion is especially simple if the bucket consumption has the "time" dimension. The PP/DS mode duration must be the same as the bucket consumption.
You are not permitted to maintain a variable duration and a variable capacity consumption in the PP/DS if you have multimixed resources. Both capacity requirement dimensions would depend on the quantity. This would lead to a quadratic dependence on the quantity for the bucket consumption. This cannot be modeled in the SNP PPM.
Mapping Alternative Modes
=================================
The generation report for SNP PPMs enables you to generate a specific number of SNP PPMs from different mode combinations contained in a PP/DS plan (SNP PPM generation with a lot size margin). The number of SNP PPMs depends on the number of activities and alternative modes of the PP/DS PPM.
In turn, SNP PPM generation without lot size margins means that exactly one SNP PPM is generated from a PP/DS PPM for a single lot size and a mode combination.
Determining The Mode Durations
===========================
SNP planning only roughly considers the durations of operations or activities. Only bucket resources are reserved in SNP. This does not depend on the duration of an activity. If, however, the SNP plan has several operations, the resources should be reserved for the correct planning periods. If the first operation of an order lasts longer than a planning period, the second operation must be scheduled in a planning period at a later stage. This shift is calculated using the mode durations in the SNP plan. The SNP PPM mode durations differ from the PP/DS PPM mode durations in the following aspects:
- The purpose of the mode duration is different. In the PP/DS PPM, the mode duration is used to determine the exact duration of an activity. In the SNP PPM, the mode duration is used to determine the planning period in which the resource is reserved.
- A lower degree of accuracy is required when you use the mode duration in SNP. The mode duration in SNP therefore cannot be maintained as a quantity-dependent mode duration either.
- The mode durations in the SNP PPM consider both the mode durations in the PP/DS PPM as well as the minimum intervals in the relationships in the PP/DS PPM.
When generating without a lot size margin, the fixed duration is calculated as follows:
For each day that is started and that requires an activity, the fixed duration is increased by one day.
When generating with a lot size margin, the system bundles the maximum number of activities that fit in a bucket (these may be all operations if you have a monthly bucket). The fixed duration of the mode is then set to one day. The bucket consumptions result from the durations of the corresponding mode.
The logic is as follows: During the SNP PPM generation without a lot size margin, a new operation is generated if the primary resource changes from one bucket to another. A new activity is generated if a secondary resource or a material changes.
During the generation with a lot size margin, the system merges as many PPDS activities for an SNP activity as the bucket specification allows. This means: If weekly buckets are used during the generation, a much larger number of activities fit into a bucket (and are therefore merged for the SNP activity) than if daily buckets were used for the SNP PPM generation.
Determining The Component Quantities
=================================
The following applies to SNP PPM generation without a lot size margin:
The variable consumptions from the PP/DS PPM are multiplied by the lot size from the initial screen for the SNP PPM generation and they are added to the fixed consumption quantity. The result is transferred to the SNP PPM as a variable quantity. The SNP PPM generation without a lot size margin cannot represent a fixed material consumption.
Linking SNP PPMs With PP/DS PPMs
========================================
The SNP plan can be linked to a PP/DS plan. This means that the system does not find any random PP/DS sources of supply when SNP orders are converted to PP/DS orders, but it creates the PP/DS orders using the PP/DS PPM that is linked to the SNP PPM.
Manually created SNP plans (PPMs) may also be linked to existing PP/DS plans (PPMs). In this case, however, the user must ensure that the manual maintenance is a logical representation and creates a correct relationship between the two plans (PPMs).
Quantity Split During Conversion
==============================
The conversion from SNP to PP/DS also entails a change in the planning semantics from the quantities per planning period that are planned in SNP to orders. You cannot expect lot sizes to be transferred 1:1 during this change. With APO Release 3.1, you can therefore split the lot size during the conversion. If several fixed lots or lots with a maximum quantity are produced in an SNP planning period, the split can be performed by noting the maximum quantities from the product master or the maximum quantities of the lot size intervals in the PP/DS PPM. The conversion creates several smaller orders with suitable lot sizes.
Selecting A Different PP/DS PPM
=============================
If you want the lot sizes to be retained (for example, if we use weekly planning periods in SNP, we also have weekly lot sizes in PP/DS), we can search for a suitable PP/DS PPM during the conversion. This is the case if you do not set the "Use SNP sources of supply" switch on the initial screen of the conversion report.
PDS Master Data Integration
The SNP PDS is not generated from a PP/DS PDS; instead, it is generated directly from R/3 or from an iPPE. This has the following advantages:
- The master data generated from R/3 can be used directly in SNP without having to go through PP/DS first.
- The transfer of data changes is simpler.
- In the production version, you can use different routings for PP/DS and SNP.
Although these advantages exist, there are also some disadvantages:
- The mode durations must be determined in the BAdI.
- In the standard system, you cannot create alternative SNP PDSs for different mode combinations.
Determining The Capacity Requirement
=================================
During the transfer from R/3 to SCM, the capacity requirements of the SNP PDSs are determined by the default implementation of the BAdI /SAPAPO/CURTO_SNP as follows: If the bucket resource has the "time" dimension, the capacity requirement is copied from the duration of the R/3 operation. If you have different dimensions for the available capacity for the bucket resource, the BAdI must be implemented differently, or you must maintain the capacity requirements manually in R/3. This option is available as of SCM Release 5.0. It is provided by transaction PDS_MAINT.
Determining Mode Durations
==========================
SNP planning only roughly considers the durations of operations or activities. Only bucket resources are reserved in SNP. This does not depend on the duration of an activity. If, however, the SNP plan has several operations, the resources should be reserved for the correct planning periods. If the first operation of an order lasts longer than a planning period, the second operation must be scheduled in a planning period at a later stage. This shift is calculated using the mode durations in the SNP plan. The required mode durations in SNP PDS must therefore differ from the mode durations in PP/DS PDS as follows:
- The purpose of the mode duration is different. In PP/DS PDS, the mode duration is used to determine the exact duration of an activity. In SNP PDS, the mode duration is used to determine the planning period in which the resource is reserved.
- A lower degree of accuracy is required when you use the mode duration in SNP.
- The mode durations in SNP PDS take into account both the mode durations in PP/DS PDS and the minimum intervals in the relationships in PP/DS PDS.
As of SCM Release 5.0, you can maintain the SNP mode durations in R/3 manually using transaction PDS_MAINT. In lower releases, the mode durations of SNP PDSs can be changed only using a BAdI. To do this, use one of the following BAdIs:
- /SAPAPO/CURTO_SNP method CIF_IMPORT in APO (change the field DUR2 in the table CT_MODES). Make sure that you copy the determination for the capacity requirements from the default implementation if you create your own implementation of this BAdI.
- CUSLNTRTO_ADDIN method CHANGE_CIF_STRUCTURES in R/3 (change the field DUR2 in the table CT_MODES)
Transferring SNP planning to the PP/DS production plan
The result of the SNP optimizer provides a plan that is finite at planning period level. However, overloads may still occur within the planning periods and for sequence-dependent setup activities. These must be corrected in PP/DS planning.
To plan the result in PP/DS planning in detail, the SNP optimization result must be transferred to a PP/DS production plan. Often, only the most important components are planned in SNP. Therefore, PP/DS must also generate complete planned orders (planned orders with all components and all required activities and resource reservations). These orders can then be used to determine the detailed dates/times and the order sequence taking into account the sequence-dependent setup activity.
The following options exist for transferring the SNP production plan to a PP/DS production plan:
- Using a horizon to separate SNP and PP/DS: You can use the conversion to transfer the SNP production plan to a PP/DS production plan.
- SNP planning and PP/DS planning are performed in different planning versions. You can use Demand Planning to transfer the SNP production plan to a PP/DS production plan.
- Using a horizon to separate SNP and PP/DS: You can use a procurement planning heuristic to transfer the SNP production plan to a PP/DS production plan.
The problem of advance production
The requirement of a product is often subject to strong seasonal fluctuations. If there are insufficient capacities within a period, the SNP optimizer or capacity leveling can shift the production to a previous period. In this period, the total number of product requirements is smaller than the total number of receipt elements planned by SNP. If this period moves to the PP/DS horizon and a PP/DS heuristic is executed, the PP/DS heuristic may adjust the receipt elements in the PP/DS horizon to the product requirements, that is, they are reduced. This destroys the stock build-up planned by SNP. At the height of the season, it is no longer possible to create sufficient receipt elements.
Therefore, one criterion for evaluating the procedures for the integration of SNP to PP/DS is the way in which the procedure supports advance production.
SNP->PP/DS conversion
First, the conversion is discussed. If you use this procedure, SNP is used to create all of the planned orders. The SNP planned orders are converted to PP/DS planned orders in a conversion process. This results in the following planning process:
- SNP planning is used to determine the sources of supply.
- You want the sources of supply selected by SNP to be transferred to PP/DS planning.
- SNP plans in planning periods (usually in weekly or monthly buckets). PP/DS plans in accordance with the lot sizes required for Execution. When SNP receipt elements are converted to PP/DS receipt elements, you want the system to distribute the receipt elements to the lot sizes required in the production.
- Planning/optimization of the sequences and the resource reservations then takes place in PP/DS.
Procedure
===========
You use transaction /SAPAPO/RRP_SNP2PPDS or the report /SAPAPO/RRP_SNP2PPDS to convert the SNP receipt elements in the PP/DS horizon to PP/DS receipt elements.
The quantities of PP/DS receipt elements are no longer changed after the conversion. No procurement planning heuristics are executed in the PP/DS. Of course, you can continue to use all procedures of detailed scheduling and all procedures used for the transfer to Execution for the PP/DS receipt elements. You can therefore use the PP/DS optimizer to schedule and reschedule the PP/DS receipt elements. You can execute DS heuristics. The PP/DS planned order can be rescheduled in the graphical planning table. This planned order can be checked using an ATP check and the conversion to a production order can be triggered in APO.
Settings
==============
This procedure requires the following settings:
- The PP/DS horizon is greater than or equal to the SNP production horizon.
- The planning procedure in the product master is set to manual planning.
- The conversion from SNP to PP/DS is carried out on a regular basis. An SNP receipt element may be split into several PP/DS receipt elements during this conversion (the system therefore creates lots that can be produced).
- You use an infinite scheduling strategy for the conversion.
- You must set an SNP planning area and a package size to convert the SNP receipt elements to PP/DS receipt elements.
- You must execute an MRP planning run at regular intervals (the conversion and the MRP planning run do not have to be performed in a specific sequence or at the same frequency).
Setting The Horizons
=========================
As of APO Release 3.1, you can select a PP/DS horizon that is larger than the production horizon. This can be put to good use here. Set a very small production horizon. This also enables SNP planning to create new planned orders in the short-term area. These new planned orders may soon have to be converted to PP/DS planned orders so that they are correctly sorted into the setup sequence. The PP/DS horizon is relevant for this. The PP/DS horizon can be larger than the SNP production horizon.
Strategy Profile For SNP->PP/DS Order Conversion
========================================================================
The purpose of the conversion is to transfer SNP planning results to PP/DS planning as accurately as possible. The system tries to adjust the PP/DS orders as closely as possible to the SNP planning requirements. The PP/DS orders are only scheduled during the conversion, but they are not planned. Heuristics, MRP ,or optimization can be used to plan the results after the conversion.
During the order conversion from SNP to PP/DS, the scheduling uses the start time or the end time from the period pattern of SNP planning (bucket).
With the "Backward" strategy setting, the system transfers the end time of a bucket and tries to schedule from the "Backwards" time towards today. During this, the working times of the resource are taken into account. If you have a finite resource and a finite strategy, the capacity utilization of the resources is also taken into account. If the working time of the resource is specified, for example, as 08:00 to 17:00, the system will try to schedule backwards from 17:00 instead of scheduling backwards from 23:59:59 (bucket finish). The search for a suitable slot on a resource ends at the beginning of the planning horizon. This is determined by the current time and the offset in the strategy profile. The beginning of the bucket is therefore ignored during backward scheduling. If the system is unable to find a sufficient gap on a finite resource between the beginning of the planning horizon and the end of the bucket, it cannot convert the SNP order using backward scheduling.
With the "Forward" strategy setting, the system transfers the start time of the first activity of an SNP order and it tries to create a PP/DS order from that time into the future. In this case, similar to backward scheduling, the capacity utilization with finite resources and the working times of the resource are taken into account. If the working times of the resource are defined as 08:00 to 17:00, the system will try to schedule a PP/DS order only after 08:00 towards the future (instead of 0:00:00 which is the start of bucket). The search for a suitable slot on a resource takes place up to any time in the future. The bucket end from SNP planning is ignored here.
If you have the planning direction "Backward with Reverse", the system creates the PP/DS order with forward scheduling if no suitable slot could be found using backward scheduling.
The planning direction "Forward with Reverse" is not useful for converting SNP planned orders. There is no point in time where forward scheduling would switch to backward scheduling.
Using a finite scheduling strategy (find slot, insert mode, squeeze in) during the conversion of SNP planned orders to PP/DS planned orders has the following disadvantages:
- A finite strategy has a negative impact on system performance.
- During the conversion of SNP planned orders to PP/DS planned orders, sequence optimization is not carried out. The scheduling result may be very poor if you use sequence-dependent setup activities and finite planning.
- The PP/DS planned orders may be scheduled in a bucket that is not the bucket SNP earmarked. In this case, SNP planning loses its significance. In addition, it becomes more difficult to check the correct modeling of capacities in SNP. For further information about this, read the section "Available Capacity in SNP and PP/DS".
We therefore recommend that you use an infinite planning strategy to convert SNP planned orders to PP/DS planned orders. The system will then create all of the orders of a bucket at the same date. After the conversion, you can improve the planning result using, for example:
- A resource heuristic
- The PP/DS optimizer
If SNP planning was carried out finitely with bucket resources and if not all planned orders can be planned in the bucket planned by SNP, the available capacity of the bucket resource may be too large. Check whether the available capacity for the bucket resource is too large.
When you make the general settings in the strategy profile, you must take the following aspects into account:
- The validity periods for the orders must be taken into account.
- The desired availability date does not influence order scheduling.
- We recommend infinite scheduling as the scheduling mode.
- The planning direction forward scheduling with reverse is not used in the conversion from SNP to PP/DS.
When you make the settings for dependent objects in the strategy profile, you must take the following aspects into account:
- You must ignore fixed and dynamic pegging.
- You must take the maximum intervals into account.
- Take into account that you must use compact scheduling.
- Relationships must always be taken into account.
These settings apply to APO Release 3.0 and 3.1.
Splitting SNP Receipt Elements
======================================================
The conversion from SNP to PP/DS also entails a change in the planning semantics from the quantities per planning period that are planned in SNP to orders. The order sizes in PP/DS are determined by technical feasibility, among other things. In many cases, the order quantity required in PP/DS will not correspond to the production quantity of a planning period.
The option of splitting lot sizes during conversion was implemented in APO Release 3.1. The following options are available:
- The quantity of the SNP planned order is transferred 1:1.
- The PP/DS planned orders are created using the fixed lot sizes from the product master.
- The SNP planned order is split up into several PP/DS planned orders, whose quantity is the maximum quantity of the PP/DS plan.
- The PP/DS lot sizes are determined in a BAdI. For more information, see Note 571118.
The smaller PP/DS orders that are generated in this way are a better basis for the requirement-synchronous production in a period.
Setting The SNP Planning Area
===================================================
Order categories are used to select the SNP orders for the PP/DS release. The order categories for the SNP orders are defined in a planning area. If a planning area is used during the conversion and this planning area does not contain any of the specified SNP order categories, the system does not select any SNP orders for the conversion.
During the order conversion, you can use the planning area to read the order categories globally from Customizing. Alternatively, you can use the planning area to select the order categories for a specific application from the initial screen of the transaction. The application-specific selection allows you to define several planning areas, which may contain different order categories. As a result, you can use different planning areas in a flexible way without making global changes in Customizing.
Setting The Package Size (APO Release 3.1)
=====================================
The packaging of the SNP orders controls system performance during the creation of PP/DS orders in the liveCache.
During this, due to the lot-size calculation, several PP/DS orders can be created simultaneously. In this case, we recommend that you reduce the package size because the number of PP/DS orders is greater than the package size of the SNP orders when an order is created; this may impair system performance during the conversion.
In large packages, conversion has a disadvantage if at least one order cannot be created during the PP/DS order creation. As a result, no SNP orders contained in the package are converted. However, the number of unconverted SNP orders and information about the quantity, availability date/time, and the location products affected are recorded in the planning log. It distinguishes between incorrect SNP orders and SNP orders that can be subsequently converted in the second run.
We recommend that you keep the package size as small as possible to ensure that the system converts as many orders as possible. However, this has a negative impact on system performance.
Alternatively, you can start the conversion twice: Once with a bundle of SNP orders in large packages (200, for example). The second time, you can start the same selection with smaller packages (package size = 1 SNP order, for example). In this way, at least those SNP orders for which no errors occurred during the PP/DS order creation are converted.
In addition, you have the option of restricting the selection to only those products that can be converted subsequently. In this way, packages can retain their original package size.
Why Do We Have To Perform An MRP Planning Run?
====================================================
You cannot use a procurement planning heuristic to plan a product that is procured using the converted SNP receipt elements. Typically, old receipt elements that no longer correspond to the current planning situation are deleted and replaced with new receipt elements for this type of procurement planning heuristic. In this case, the selection of sources of supply (source selection) for the old receipt element is lost. From a cost point of view, however, the selection of sources of supply is one of the most important advantages of using the SNP optimizer. If you want to retain this selection of sources of supply, you cannot execute procurement planning heuristics in PP/DS.
The planning procedure also determines whether the existing planned orders are exploded again when you change the plan (PPM or PDS). It is very useful to explode PP/DS planned orders again when the plans are changed. This is set in standard Customizing of the "Manual planning" planning procedure). Only one planning file entry is created for the new explosion when changes are made to plans. The actual new explosion occurs in the MRP planning run. An MRP planning run is therefore also required in this scenario.
Disadvantages Of Conversion
=======================
The disadvantages of converting from SNP to PP/DS are as follows:
- The PP/DS receipt elements are not adjusted to the changed requirements.
- There is no make-to-order production.
- There is no PP/DS lot-size calculation.
The PP/DS Receipt Elements Are Not Adjusted To Changes In Requirement
==============================================================
In this integration scenario, all new receipt elements are exclusively created by SNP. In this way, you can ensure that the SNP source of supply determination is always used. On the other hand, only SNP planning performs the downwards adjustment of receipt quantities when requirements are reduced. However, since PP/DS receipt elements are fixed for SNP planning, this is not always possible in the suitable bucket. If a requirement is reduced within the PP/DS horizon (and if all of the SNP receipt elements within the PP/DS horizon have already been converted to PP/DS receipt elements), SNP planning is unable to adjust the receipt elements that cover the requirement. Instead, the system has to reduce SNP receipt elements in a later period so that the total number of receipt elements and requirements is correct again. The PP/DS receipt elements then cover requirements outside the PP/DS horizon.
There Is No Make-To-Order Production
===========================
Make-to-order production is not possible. SNP generates all receipt elements and only converts them to PP/DS receipt elements at a later stage. SNP planning does not support the make-to-order production.
Lot-Size Calculation In PP/DS
==========================
If the PP/DS receipt elements are created using conversion, the system cannot perform the PP/DS lot-size calculation. The lot sizes of PP/DS receipt elements are not related to the requirements in the PP/DS horizon. Lot-for-lot order quantity and periodic lot sizes are not supported.
Advantages
===========
- Lot-size intervals from the PPM are used.
- Advance production is possible.
Lot-Size Intervals From The PPM Are Used
===============================================
A common problem, particularly in process industries, is that alternative resources require different lot sizes in production. For example, a specific product can be produced in a reactor that can hold 1,000 liters or in a reactor that can hold 500 liters. Both alternative resources have alternative plans (PPMs) with different lot-size intervals. These alternative resources cannot be planned in the PP/DS procurement planning heuristic delivered by SAP or in the SNP heuristic. The reason for this is:
The heuristics execute the planning subfunctions in a specific sequence. During this, the system always determines the lot sizes first. Afterwards, the system carries out a selection of sources of supply. During this, the previously determined lot sizes have a restrictive effect on the selection of sources of supply. If, in the above example, the lot-size calculation determines a lot size of 1,000 liters, the production can only take place on the first reactor. If, on the other hand, the lot-size calculation determines a lot size of 500 liters, production can only take place on the second reactor.
The SNP optimizer can correctly plan alternative sources of supply with different lot-size intervals. In the above example, if the requirement is 1,000 liters, the SNP optimizer either creates an order for 1,000 liters with the first plan or two orders with the second plan, depending on the costs and the utilization of the resources. The result of the SNP optimizer can be transferred by converting SNP orders to PP/DS orders.
Advance Production And Deliberate Delays
================================================
One result of SNP planning may be a requirement, which you want to cover several planning periods earlier using an advance production. In particular, this is often the case if the requirements undergo seasonal fluctuations. By considering storage costs and the costs for alternative sources of supply, the SNP optimizer can determine an optimal stock policy for the most important products.
SNP planning may decide to use a scarce resource to manufacture a product with a high added value first, and to manufacture another product competing for the same resource later.
If a separate procurement planning heuristic is executed in PP/DS planning, these SNP planning decisions may be destroyed.
The PP/DS procurement planning heuristics work on the assumption that requirements are covered as soon as possible. These heuristics do not recognize that a receipt element is intended to cover a requirement outside a time interval determined by the lot-sizing procedure. If the receipt element is within the PP/DS horizon but the requirement is outside the PP/DS horizon and outside the time interval determined by the lot-sizing procedure, the PP/DS procurement planning heuristic deletes the old receipt element and does not replace it with a new receipt element. If the peak of the season is reached, even PP/DS planning must recognize that the requirements cannot be covered immediately.
If the conversion from SNP to PP/DS is used, the dates/times determined by SNP planning are retained. The problems regarding the procurement planning heuristic do not occur.
SNP and PP/DS in different planning versions
Planning Process
==============
- Central SNP planning is used to determine production plants and target stock levels and to carry out a rough feasibility check. SNP planning is performed in a planning version not equal to "000".
- Central SNP planning is copied to planning version "000". Here, it acts as the production program for PP/DS planning in the form of planned independent requirements. The production, that is, PP/DS planning must cover these planned independent requirements.
- Due to these planned independent requirements, PP/DS planning is carried out decentralized.
- For incoming sales orders, the ATP check can be used to take the sales order from the production plant that contains unconsumed forecast or free receipt elements.
- The sales orders are offset against the planned independent requirements. The chronological distribution of the production program changes. A new PP/DS planning run can adjust the receipt elements to these changes.
- Planning/optimization of the sequences and the resource reservations then takes place in PP/DS.
Procedure
==========
You copy stocks, fixed PP/DS planned orders and fixed purchase requisitions, production orders, and purchase orders (that is, all objects that can no longer be changed in PP/DS planning) from the active planning version to the SNP planning version. You use transaction /SAPAPO/VERCOP to copy the version.
You execute SNP planning in the usual way in a planning version not equal to "000".
Once you are happy with the SNP planning result, you transfer the production plan to Demand Planning using transaction /SAPAPO/LCOUT.
Using transaction /SAPAPO/MC90, the planned independent requirement that is required is generated from the Demand Planning key figure that is determined in this way.
You can use either transaction /SAPAPO/LCOUT or transaction /SAPAPO/MC90 to change the planning version. You must copy "000" to the target planning version for one of the two copy operations.
In planning version "000", you execute PP/DS planning with the usual tools, such as background scheduling using transaction /SAPAPO/CDPSB0.
Planning Version Settings
=============================
In the planning version (transaction /SAPAPO/MVM), you can make settings that prevent safety stocks from being taken into account in PP/DS planning. The safety stocks were already considered during planning in SNP. Otherwise, the safety stocks are taken into account twice, once in SNP and once in PP/DS. The result of this planning is transferred to PP/DS. In planning version "000", you must therefore set the PP/DS indicator for taking the safety stock into account to its default value.
In the SNP planning version, you can deactivate the creation of planning file entries for PP/DS. This indicator has no effect unless a PP/DS planning run is started in this planning version or an MRP heuristic is carried out in the planning version. However, system performance is improved if no unnecessary planning file entries are created. We therefore recommend that you do not set the indicator for "PP/DS: Change planning active" in the SNP planning version.
Conversely, you can deactivate the creation of planning file entries for SNP in the active planning version "000". In the planning version "000", do not set the indicator for "SNP: Change planning active".
In planning version "000", PP/DS change planning is active.
In the SNP planning version, SNP change planning is active.
Requirement Strategy Settings In The Product Master
==================================================
A PP/DS procurement planning heuristic initially covers the planned independent requirements that were generated from SNP planning. These planned independent requirements can be consumed against sales orders at a later stage. Requirement strategy 20 and the consumption period must be set in the product master for this purpose.
Very often, the production plants will have to not only cover the sales orders, but also stock transfers to other plants or dependent requirements arising from further processing of the product. In this case, we require what is called "subassembly planning".
Set the subassembly planning as follows:
You require a category group containing the categories of all requirements against which planned independent requirements are to be offset. You create the category group using transaction /SAPAPO/SNPCG. Depending on what you require, the category group contains categories for sales orders, dependent requirements, and stock transfer requirements.
Afterwards, create a new requirement strategy in Customizing (transaction SPRO, menu path: SAP APO -> Master Data -> Product Master -> Specify Requirements Strategies). If planned independent requirements have the category "FA" and the assignment mode "1", they are offset against all categories from the new category group.
Set the indicator for subassembly planning in the product master and set the new requirement strategy.
Version Copy Settings
===============================
The version copy is executed using transaction /SAPAPO/VERCOP. Copy the master data and the transaction data and select the checkbox for the order data. You must at least specify the categories for stocks, production orders, purchase orders, firmed planned orders, and fixed purchase requisitions.
All receipt elements that are fixed for PP/DS planning must be copied to the planning version of SNP planning for the following reason:
If the receipt elements are not copied, SNP planning does not know about these receipt elements. In this case, SNP planning creates new SNP receipt elements to cover the requirements for the product. Very often, these new SNP receipt elements have another source of supply and will utilize other resources. SNP planning and PP/DS planning start to deviate from each other.
The SNP optimizer can plan stock transfers and the production in a way that ensures optimum use of existing fixed receipt elements. Of course, this is particularly useful when the requirements and the fixed receipt elements are in different locations. The fixed receipt elements must also be known to SNP planning in this case.
Stock Transfers
============
In the scenarios described above, the sales orders are returned directly from the production plants. This is the simple scenario. The ATP check selects the production plant.
If the sales orders are delivered from distribution centers and if there are possibly several alternative production plants for supplying a distribution center, stock transfer purchase requisitions must be created for supplying the distribution center. You have the following options for this:
- As of APO Release 3.1, the rules-based ATP check allows you to carry out multilevel checks and to create stock transfers, if required. In this case, the ATP check first checks the availability in the distribution center. If there is no availability in the distribution center, the ATP check identifies other possible location substitutions. In the master data of the rules-based ATP, location substitutions are maintained between the distribution center and the production plant. After this, the ATP check checks the availability in the production plant. If there is availability in the production plant, the ATP check creates a stock transfer between the production plant and the distribution center. For this purpose, set the "Stock Transfer" activity for the location product substitutions in integrated rule maintenance (transaction /SAPAPO/RBA04).
- You can use deployment to distribute the surpluses from the receipt elements in the production plants to the distribution centers.
- As of APO Release 4.0, you can copy SNP receipt elements from an inactive planning version to the active planning version. Transaction /SAPAPO/VERMER or report /SAPAPO/VERSION_MERGE are provided for this. Using this transaction, you can copy SNP stock transfers from the planning version for SNP planning to the operative planning version "000". In planning version "000", you can either transfer these SNP stock transfers directly to the OLTP system (for example, an R/3 system) or convert them to PP/DS stock transport requisitions. The advantage of converting them to PP/DS stock transport requisitions is that you can then restrict the purchase requisitions being transferred to R/3 to purchase requisitions within a certain timeframe.
Advantages Of Planning In Separate Planning Versions
================================================
Executing SNP planning and PP/DS planning in different planning versions has the following advantages:
- There is a high degree of stability in SNP planning.
- Checked SNP plans are released to PP/DS
- SNP planning and PP/DS planning are performed at their own frequency.
- Distribution to several APO systems is possible (in theory).
- Stock build-up is enabled in SNP.
- Adjusting the production to the requirements is possible.
- Make-to-order production is possible.
- There are no restrictions for periodic lots in PP/DS.
Stability Of Planning
======================
SNP planning is frequently used for medium-term to long-term time frames. With these time frames, it does not always make sense to include all current changes to the actual data immediately in SNP planning:
- The SNP planner often wants to create and compare several alternative plans. However, these plans can only be compared if no changes were made to the basic requirement data between the creation dates of the plans.
- A group of SNP planners works simultaneously on creating subplans for individual product groups, geographical regions, and so on. These subplans are later merged into an overall plan. The same determining factors that were taken into account in creating the partial plans must also apply in evaluating the quality of the overall plan.
If you execute SNP planning in your own planning version, you can select the time of the version copy and thus specify exactly which data is included in SNP planning and how often the data is updated.
Checked SNP Plans Are Released To PP/DS
=====================================
If you execute SNP planning and PP/DS planning in the same planning version, all changes in SNP planning are immediately taken into account in PP/DS planning. If, for example, an SNP planned order generates a dependent requirement for a component within the PP/DS horizon, a PP/DS planning run will try to cover this dependent requirement. However, in many cases this measure may be premature because the SNP planned order will be changed several times.
If SNP planning and PP/DS planning are executed in different planning versions, you have the option to release only checked, reconciled, or approved SNP plans to PP/DS planning.
SNP Planning And PP/DS Planning Are Performed At Their Own Frequency
==========================================================
As mentioned above, SNP planning is a period-based planning function and the intervals used to execute SNP planning are often based on these planning periods. PP/DS planning, in contrast, operates so that it is accurate to the second and should therefore be executed far more frequently.
As long as SNP planning and PP/DS planning are carried out in different planning versions, each planning can operate at its own frequency.
Distribution Across System Boundaries
=============================
The BAPI "PlanningBookAPS" is one of the building blocks which allows SNP planning and PP/DS planning to be carried out on different APO systems. For this, the time series from Demand Planning are exchanged between the systems.
All other alternatives discussed here execute SNP planning and PP/DS planning in the same planning version. Distributing the functions across different computers is not possible in this case as a matter of principle.
Stock Build-Up Is Enabled In SNP
=============================
If SNP planning wants to execute a stock build-up to cover a seasonal requirement that occurs at a later stage, this stock build-up is transferred to PP/DS planning. This occurs on the condition that the SNP receipt elements are transferred to Demand Planning using transaction /SAPAPO/LCOUT. Only SNP receipt elements show the stock build-up. Another condition is the creation of planned independent requirements with final assembly using transaction /SAPAPO/MC90. These are the only requirements that allow advance production.
Adjusting The Production To The Requirements Is Possible
===========================================
Planned independent requirements are generated from the result of SNP planning. These planned independent requirements are consumed with sales orders, and dependent requirements and stock transfer requirements for the same product, if applicable. The planned independent requirement is reduced and the sales order, the stock transfer requirement, or the dependent requirement is taken into account for the requested delivery date or the requirement date/time. This changes how the requirements are chronologically distributed. A new PP/DS planning run takes account of this change in distribution.
All sales orders are taken into account in PP/DS planning even if the total of sales orders exceeds the quantity planned using planned independent requirements. In this case, an adjustment in relation to the confirmed requirements also takes place in PP/DS planning.
However, automatic adjustment (reduction) of the planned production does not occur where the quantity planned using planned independent requirements exceeds the total of sales orders and any stock transfer requirements and dependent requirements. Stock build-up would not be possible either if the planned production was adapted to the confirmed requirements in this case.
If you do not want to use the stock build-up, you have two other options for handling a situation in which the quantity of planned independent requirements exceeds the total of sales orders:
- As of APO Release 3.1, you can use the conversion rule to check whether a planned order or purchase requisition is actually required for a sales order. If the planned order or purchase requisition only covers a planned independent requirement, conversion to a production order or purchase order is not possible. The check takes place on several levels.
- Requirement strategy 30 is set in the product master. The system then generates planned independent requirements for planning without final assembly. To cover these planned independent requirements, a PP/DS procurement planning heuristic creates planned orders or purchase requisitions which cannot be converted into production orders or purchase orders. The "Planning without Final Assembly" function cannot be inherited to lower assemblies. You can therefore prevent final assembly only at finished product level. Therefore, we recommend the conversion rule.
Make-To-Order Production Is Possible
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The planned independent requirements created using SNP planning can also be consumed with sales orders for make-to-order production. For this purpose, you must use a requirement strategy with assignment mode "2" in the product master. Usually, requirement strategy 30 (planning without final assembly) is used. If you want to combine make-to-order production with the option of stock build-up, you need a planned independent requirement for the planning with final assembly. For this purpose, create a separate requirement strategy with planning segment initial and assignment mode #2'.
Disadvantages:
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Planning SNP and PP/DS in separate planning versions has the following drawbacks:
- The SNP source selection can not always be transferred.
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By defining alternative plans, you can model and plan alternative resources within a production plant in SNP. SNP planning generates planned orders with different sources of supply or plans. All these planned orders are aggregated to a single key figure in the Demand Planning. In this case, PP/DS planning no longer possesses any information about the resource selection in SNP. As a result, only the source selection at a higher level, that is, at production plant level, can be transferred to PP/DS planning.
PP/DS MRP with standard lot size heuristic
Converting SNP receipt elements to PP/DS receipt elements has some disadvantages:
- The PP/DS receipt elements are not adjusted in relation to changed requirements within the PP/DS horizon.
- Make-to-order production is not possible.
- Restrictions apply to the lot-sizing procedures.
Often, users try to avoid the disadvantages of converting SNP receipt elements to PP/DS receipt elements by carrying out both a SNP planning run and a PP/DS planning run (with a standard lot size heuristic, for example) in the same planning version. The standard lot size heuristic in PP/DS can handle make-to-order production it can adjust PP/DS receipt elements to changed requirements. In this case, why not simply combine the two planning procedures? The new objectives are:
- SNP plans in buckets (generally in weekly or monthly buckets). PP/DS plans in accordance with the lot sizes required for Execution. Planning with the PP/DS MRP distributes the quantities planned by SNP into lots that can be produced.
- The PP/DS receipt elements are adjusted in accordance with the changed requirements.
- SNP always plans for make-to-stock production. However, you want some of the sales orders to be covered by make-to-order production. SNP planning works on the basis of planned independent requirements. The forecast consumption is set so that these planned independent requirements are reduced by make-to-order sales orders. Instead, MRP planning in PP/DS is supposed to create planned orders for make-to-order production.
Algorithm
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The procurement planning heuristics in PP/DS, such as the standard lot size heuristic, carries out the following steps consecutively for each product:
- The receipts and the requirements are read.
- Net requirements calculation is executed for all fixed receipts and requirements. SNP receipts outside the PP/DS horizon are fixed to prevent them from being changed by PP/DS.
- Lot-size calculation is carried out for all outstanding requirements.
- The reusability is checked for old unfixed receipts.
- Old receipts that have not been reused are deleted (SNP receipts outside the PP/DS horizon were fixed and are therefore not changed).
- New PP/DS receipts are created if the date/time falls within the PP/DS horizon.
Settings
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The procedure requires the following settings:
- Standard lot size heuristic in the product master (or default value from the planning procedure)
- "Planning in Planning Run" planning procedure in the product master on the PP/DS screen
- Infinite scheduling strategy for the MRP planning run (setting in the procurement planning heuristic as of APO Release 4.0 or using transaction /SAPAPO/RRPCUST1).
- Net requirements calculation using the first in first out (FIFO) strategy (you can set this in the procurement planning heuristic)
- Net requirements calculation on requested quantities (you can set this in the procurement planning heuristic)
- For periodic lots in PP/DS, the planning periods in SNP must be greater than or equal to the periods for the creation of lots in PP/DS. The period limits for the SNP planning periods are also the period limits for PP/DS lot-size creation.
- Safety stocks are taken into account in the PP/DS planning (you can set this in the planning version using transaction /SAPAPO/MVM).
- PP/DS horizon is initial.
- Delays are permitted in SNP planning (you can set this in the product master on the screen SNP1).
- An SNP planning run must be executed immediately before each MRP planning.
Net Requirements Calculation Using FIFO Strategy
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If the default settings are used for the net requirements calculation in PP/DS, the net requirements calculation first uses fixed receipt elements to cover later requirements. This also occurs if the requirement is outside the PP/DS horizon and we would expect it to be covered by the SNP planning function. If the fixed receipt is used for later requirements, an earlier requirement may remain uncovered. The PP/DS heuristic creates a new receipt element for this requirement. If the requirement was already covered by an SNP receipt element outside the PP/DS horizon, this SNP receipt element becomes a surplus (until the next SNP planning).
To solve this problem, you must ensure that the delayed fixed receipt covers the preceding requirement. You have the following options:
- The net requirements calculation is carried out using the FIFO strategy. The relevant settings are made in the standard lot size heuristic. In APO Release 3.0 and 3.1, you must set the "Consider Fixed Receipts First" indicator for the FIFO strategy. In APO Release 4.0, set the procedure for the net requirements calculation to "FIFO". Refer also to Note 448960.
- If you use the net requirements calculation, a delayed fixed receipt is also assigned to a requirement if the difference is smaller than the alert threshold for delays. The alert threshold for delays is set in the product master on the requirements screen.
Why Must Delays Be Allowed In SNP Planning?
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If a FIFO strategy is set for the net requirements calculation and if delays in SNP are not permitted, the effect is as follows:
PP/DS planning creates receipt elements for the requirements within the PP/DS horizon. However, some of these elements are delayed. The delayed receipt elements are not used by the SNP net requirements calculation to cover the earlier requirements. The delayed receipt elements are therefore available for requirements outside the PP/DS horizon. These requirements are neither covered by PP/DS planning nor by SNP planning.
You set the maximum delay for the SNP optimizer in the product master on screen SNP1.
The net requirements calculation in PP/DS and SNP should return the same result if PP/DS and SNP are to cover the same requirements.
Why Perform The Net Requirements Calculation On Requested Quantities?
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In SNP planning, planning is usually executed for requested quantities. In the PP/DS standard lot size heuristic, you can choose between planning with requested or planning with confirmed quantities in the sales order in APO 3.0 and 3.1. The following problems may occur if you configure that PP/DS planning is carried out on the basis of the confirmed quantities:
- A sales order is entered but it is not confirmed. SNP planning creates receipt elements based on the requested quantity in the sales order. If the sales order moves to the PP/DS horizon, PP/DS planning no longer recognizes the requirement from the sales order. In this case, PP/DS planning deletes the SNP receipt element, but it does not create its own PP/DS receipt. As a result, the next SNP planning must create a receipt again to restore the quantity balance from the SNP planning point of view. The planning function constantly switches between two statuses.
- In this scenario, SNP planning and PP/DS planning are performed on the same requirements. The total requirements comprise sales orders, dependent requirements, stock transfer requirements, and planned independent requirements. The planned independent requirements are usually consumed against the sales orders. The system can carry out this consumption either with the requested quantity or with the confirmed quantity. The setting for the forecast consumption must correspond to the planning setting. The forecast consumption allows only one setting.
Why Does The PP/DS Horizon Have To Be Initial?
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The net requirements calculation carried out in SNP is different to the calculation performed in PP/DS. In SNP, all requirements for a planning period (bucket) are covered by the receipt elements in the same planning period. To cover new requirements within a planning period, SNP planning often creates a receipt element in the middle of or at the end of the planning period. This always occurs in SNP for daily periods and depending on the period factor for other planning periods. In contrast, receipt elements in PP/DS must be available before the requirement for it to be covered.
This causes the following problem: SNP planning created an SNP receipt within or at the end of the planning period to cover a requirement at the start of the planning period. From the PP/DS point of view, the requirement appears to occur before the receipt element. Therefore, the requirement cannot be covered by the existing SNP receipt element.
If both the SNP receipt element and the requirement are within the PP/DS horizon, PP/DS planning simply deletes the SNP receipt element and creates a new PP/DS receipt element. The receipt elements total then corresponds again to the requirements total. There is no sign of the problem.
However, if the requirement is within the PP/DS horizon and the SNP receipt element is outside the PP/DS horizon, PP/DS planning must not delete the SNP receipt element. Unnecessary SNP receipt elements are present until the next SNP planning.
This is particularly irritating if these SNP receipt elements generate dependent requirements. The system can no longer tell whether dependent requirements have originated from SNP or PP/DS. In this case, it is likely that too many component requirements will be procured.
To avoid this problem, let the PP/DS horizon always move on by one planning period. The PP/DS horizon moves on by one planning period each time if the following conditions are met:
- You use APO Release 4.0.
- In addition, the PP/DS horizon is initial. If you have an initial PP/DS horizon, the SNP production horizon applies as the default value for the PP/DS horizon.
What Is To Be Considered When Using Periodic Lots In The PP/DS?
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For periodic lots, you expect the system to cover all requirements within a period using a single receipt element. If part of the period falls outside the PP/DS horizon, the system also expects all requirements (inside or outside the PP/DS horizon) to be covered by a single PP/DS receipt element. If the system had to increase the PP/DS planned order during the period by the quantities of the additional requirements trickling into the PP/DS horizon, all planning actions already carried out with this PP/DS receipt element would be invalidated. In this case, the user would have to repeat a scheduling run, rescheduling, campaign assignment, ATP check, and so on.
If the requirements were in different SNP planning periods, the part of the PP/DS lot size period outside the PP/DS horizon would still be covered by user-defined SNP receipt elements. Accordingly, the shortage for the PP/DS would be smaller. PP/DS planning could cover only part of the requirements in the period.
Therefore, the following conditions are required: Firstly, the PP/DS horizon must move on by SNP planning periods, and secondly, the periods for PP/DS lot-size calculation must not be greater than the planning periods.
The period boundaries of the SNP planning periods must be the same as the limits of the periods used in the PP/DS lot-size calculation. If monthly periods are used in SNP, the lot-size calculation can create daily lots, 10-day lots, or monthly lots in PP/DS, but it cannot create weekly lots because Mondays usually do not fall on the first day of a month. If weekly periods are used in SNP,
daily or weekly lots can be used in PP/DS.
Why Must SNP Planning Be Executed Before The MRP Planning Run?
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The PP/DS horizon is relevant only for make-to-stock production. For make-to-order production, the entire time axis is within the PP/DS horizon. A make-to-order sales order outside the PP/DS horizon reduces the planning quantity and acts as a separate requirement element for the MRP planning run. MRP planning covers this requirement using a new planned order. If no SNP planning run is executed previously, the SNP planned order still contains its original quantity for the make-to-stock production. The quantity of the SNP planned order is too large. The combined totals of SNP planning and PP/DS planning constitute an overproduction. Too many components are procured and too many resources are reserved.
Disadvantages
==========
- The SNP selection of sources of supply is lost.
- There are restrictions for periodic lots.
- Advance production (early build) is not possible, or it is only possible with restrictions.
- The planning process is complicated.
- There is a lack of transparency.
The SNP Selection Of Sources Of Supply Is Lost
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During this procedure, the SNP orders are deleted by the MRP heuristic in the PP/DS horizon. Instead, the MRP heuristic creates PP/DS receipt elements to cover the requirements within the PP/DS horizon. The PP/DS receipt elements are in no way related to the original SNP orders. The source selection of the SNP order cannot be transferred to the PP/DS order. The PP/DS heuristic carries out its own source selection which, of course, returns a result that differs from the SNP planning result.
This is only a problem if alternative sources of supply actually exist for the product. It is not a limitation if single sourcing is used. However, it is a serious limitation if alternative sources of supply are available. After all, SNP planning is carried out specifically to optimize the selection of sources of supply. If the results from this planning cannot be copied to PP/DS planning, the entire SNP planning run serves no purpose.
You could try to avoid this drawback by converting SNP planned orders to PP/DS planned orders between the SNP planning run and the PP/DS planning. However, this will not stop PP/DS planning from performing a new source selection. PP/DS planning always carries out a new source selection if a quantity or date/time for the converted planned order does not match the requirement. The planning process is complicated further by the additional conversion.
Advance Production (Early Build)
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Of course, SNP planning can meet a future requirement with an earlier procurement. This option is particularly useful for seasonal fluctuations in requirements and limited capacities. Depending on the storage and procurement costs, the SNP optimizer can find a solution which allows the requirements from a future period to be covered using a production in an earlier period. The procurement planning heuristics provided by SAP in PP/DS, on the other hand, can support only requirement-synchronous procurement. If the requirement is outside the PP/DS horizon but SNP has scheduled a receipt within the PP/DS horizon, the standard lot size heuristic would delete the SNP receipt from the PP/DS horizon without replacing it.
To solve the problem, some PP/DS heuristics have an indicator for taking into account shortages outside the production horizon. If this indicator is selected, the PP/DS heuristic adds up all shortages outside the PP/DS horizon and within the period specified in the heuristic. Due to the limited resources available, SNP cannot cover these shortages itself and expects these product requirements to be covered by receipt elements in the PP/DS horizon.
If you want to retain a stock build-up planned by SNP, you must ensure the following aspects:
- Select the indicator for taking account of shortages outside the production horizon in the PP/DS heuristic. The horizon should include a seasonal cycle.
- The SNP and PP/DS planning runs must be carried out in the correct sequence. SNP planning must always be executed first.
If the indicator for taking account of shortages outside the production horizon is set, all shortages in the specified period are added up and moved to the end of the PP/DS horizon. There, they are treated as ONE requirement. If there is an exact lot size, the entire stock build-up is carried out by a single receipt element. This receipt element may be very large and therefore difficult to deal with or difficult to plan. Check whether a maximum lot size can be used to cover the requirement using several receipt elements.
The Planning Process Is Complicated
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As described above, an SNP planning run must be executed before every PP/DS planning run. This is not how an ideal planning run is expected to work.
SNP planning is a long-term and period-based planning system. The planning periods in SNP are often weeks or months. From an SNP point of view, there is no reason to execute SNP planning more often than once per planning period. This is unless the previous period was so poorly planned that the actual data differs significantly from the planned data and this actual data is to be taken into account in SNP planning.
System administration is also complicated by the interdependencies between the planning runs. Ideally, the sequence of planning runs should be variable.
In a system with 7*24 hour availability, it is even necessary for each planning run to store a consistent overall plan when it is completed because the planning results may be read at any time. This requirement cannot be met by integrating SNP and PP/DS with the approach described.
Lack Of Transparency
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During the conversion from SNP to PP/DS, conflicting objectives may arise. The objectives of SNP and PP/DS will contradict each other if SNP tries to avoid seasonal capacity overloads using an advance production and at the same time, PP/DS only releases production if the sales order is already available or PP/DS executes a make-to-order production or PP/DS always adapts the planning to sales orders.
If SNP planning and PP/DS planning are executed in separate planning versions, the planning results of both plans are always available and comprehensible (as far as the optimizer allows). If there are conflicting objectives, the SNP planner and the PP/DS planner can use their respective planning results for the required adjustments.
If SNP planning and PP/DS planning are carried out in a single planning version, there is a risk that the SNP planning result is destroyed by PP/DS planning (at least within the PP/DS horizon). As a result, the results of SNP planning are no longer comprehensible and they can no longer be used for a reconciliation between the planning levels that may be required.
Functions that behave differently in SNP and PP/DS
Safety Days' Supplies
======================
SNP and PP/DS treat safety days' supplies differently. In SNP, the following logic applies: In period n, cover the requirements of periods n to n+safety days' supplies. In PP/DS, the following logic applies: Cover the requirements from period n in period n-safety days' supply. If the safety days' supply is static, these two logics differ only for the period from the current point of time until the end of the safety days' supply. SNP creates only one receipt element for this period, while PP/DS may create several receipt elements (provided that there are several requirements in this period and lot size grouping does not take place). The differences are greater for time-dependent safety days' supplies. SNP uses the following logic: In period n, cover the requirements of periods n to n+safety stock(s)". SNP uses the safety days' supply at the time of the receipt element. PP/DS uses the following logic: Cover the requirements from period n in the period n-safety days' supply (or safety days' supplies). PP/DS uses the safety days' supply at the time of the requirement element.
Solution
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Header Data
| Release Status: | Released for Customer |
| Released on: | 22.03.2010 13:43:46 |
| Master Language: | German |
| Priority: | Recommendations/additional info |
| Category: | Consulting |
| Primary Component: | SCM-APO-PPS-SNP Conversion SNP to PP/DS |
Affected Releases
Release-Independent
Related Notes
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