Sunday, May 10, 2009

Safety Stock Planning

The standard methods of safety stock planning are used to build stock on hand
according to the safety stock values that you define in the location product master,
depending on previous experience. In contrast to model-based safety stock planning, forecast errors are not considered when you use the standard methods. You can maintain the safety
stock value as a static or time-dependent value. You can change the safety stock
values manually in interactive Supply Network Planning.

The advanced methods of safety stock planning are used to calculate the
time-dependent safety stock for finished products and components. In this type
of planning, the system takes into account the demand forecasts and forecast
errors within your supply chain.

Supply Network Planning (SNP) allows you to consider the actual supply
when planning safety stock. This means that, not only can the system take
forecast demand and actual demand into account, but it can also consider the
deviations between the planned Replenishment Lead Time (RLT) and the actual
Replenishment Lead Time.

The calculated safety stock is displayed in an SNP key figure in interactive
planning and can be changed manually or copied into another planning version, if
required. The calculated safety stock can also be used in both Production Planning
and Detailed Scheduling (PP/DS) and in Capable-to-Match.

If you keep safety stock both in the plant and in Distribution Centers (DCs), the
system uses the model-based calculation to take this into account. The system
always calculates the replenishment lead time starting from the last safety stock
leading location.

Calculating Safety Stock
Safety Stock Calculation Methods
• Available safety stock methods:
– SB Safety stock from location product master
– SZ Safety days' supply from location product master
– SM Maximum of SStk and SZ from location product master
– MZ Safety days' supply (maintained on a time-dependent basis)
– MB Safety stock (maintained on a time-dependent basis)
– MM Maximum of MB and MZ (maintained on a time-dependent basis)
– ATα service level and reorder cycle method
– ASα service level and reorder point method
– BTβ service level and reorder cycle method
– BSβ service level and reorder point method
If you want to use the standard methods (methods 1-3), go to the lot size tab page
of the location product master and enter the relevant data in the following fields:
• Safety stock
• SB method (safety stock method)
• Safety days' supply

To manually create safety stock on a time-dependent basis (methods 4-6), use a
macro to enter the safety stock or safety days' supply - on a time-dependent basis -
in the interactive planning table of SNP, and save the SB method on the lot size tab
page of the location product master. Mass maintenance of time series was put in
place for Release SCM 4.1 (transaction /SAPAPO/TSKEYFMAIN). Time-dependent safety stocks are stored in time series of the key figure
9ASAFETY. If you also want to plan these stocks in PP/DS, you must
assign this key figure in PP/DS Customizing.

The advanced methods of safety stock planning take the accuracy of Demand
Planning forecasts into account. To calculate the safety stock, you need to enter the demand planning key figures of your planning area that contain both past forecasts and realized demand.
The forecast errors are determined from the past data. Safety stock planning uses
relative forecast errors and the relationship from forecast errors and forecasts,
which can differ from one time bucket to the next. For the realized demand, select a key figure that contains the actual demand realized. These values can be updated from sales orders or invoiced sales quantities, etc., from the OLTP systems. For the planned demand, select a key figure that contains the forecast figures generated in the past.

As an alternative, errors for forecasts and replenishment lead times can be predefined in the location product master record (on the Lot Size tab page).

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