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Function documentationSafety and Target Stock Level Planning in PP/DS

 

In Production Planning and Detailed Scheduling (PP/DS) you can take safety stock and target stock levels into account during planning.

Safety stocks are intended to balance out unforeseeable requirements, due to forecasting errors, breakdowns in production, or seasonal fluctuations in requirements.

In PP/DS, there are two different methods with which safety stocks can be taken into account:

  • To cover unexpectedly high requirements, use the method with virtual safety stock elements. In this method you can use both static and time-dependent safety stock methods.

  • To resolve delays or problems in production, use the method with real safety stock requirements. In this method you can only use static safety stock methods.

The methods differ in regard to pegging as well as to the alerts that are generated. With both methods, a safety stock level exists in PP/DS once the planning run has been carried out. You can choose to be informed by alert if the stock level falls below the safety stock level.

You use the target stock level to cover sporadic requirements or to smooth out production, for example, if you continuously have both small and large requirements. You use it to represent the availability of safety stock in SAP APO. The target stock level is a value for the available warehouse stock level that you want to reach through planning.

You can choose to be informed by alert if the target stock level is violated. For example, you can use the alert Stock Exceeds Target Stock Level if your target stock level is the maximum capacity of your warehouse).

Prerequisites

Master Data

Planning version

In the planning version you define how PP/DS takes safety stocks into account. In the menu, choose Start of the navigation path Master Data Next navigation step Planning Version Management Next navigation step Model and Version Management End of the navigation path. In the PP/DS area, under Take Safety Stock into Account, specify which methods you want to use.

You have the following options:

  • Do Not Consider Safety Stock (’ ’)

  • Consider Virtual Safety Stock Elements (2)

  • Consider Safety Stock Requirements in SAP liveCache (3)

Note Note

You should note that many target stock methods calculate the target stock on the basis of the safety stock. If you want to use a target stock level in planning, you must choose a suitable safety stock method.

End of the note.

Product master

In the product master, on the Lot Size tab page, enter the necessary data. (Start of the navigation path Master Data Next navigation step Product End of the navigation path)

  1. Static safety stock

    Enter the safety stock level and choose a suitable safety stock method (SStk Method). In PP/DS you can use the following static safety stock methods:

    • Safety Stock from Location Product Master (SB)

    • Maximum of Safety Stock and Safety Days' Supply from Location Product Master (SM)

      Note Note

      The static safety stock maintained in SAP ERP in the material master, on the MRP 2 tab page, is copied to SAP APO when the material master data is transferred. (The safety time (actual range of coverage) becomes the safety days’ supply in SAP APO.)

      The percentage value of the availability of the safety stock, which can be defined in ERP in Customizing for Consumption-Based Planning, has not been integrated into SAP APO.

      End of the note.

  2. Time-dependent safety stock

    i. Choose a suitable safety stock method in the product master (SStk Method). In PP/DS you can use the following time-dependent safety stock methods:

    • Safety Stock (Time-Based Maintenance)(MB)

    • Maximum of Safety Stock and Safety Days' Supply (Time-Based Maintenance) (MM)

    ii. In Customizing for PP/DS, define the following:

    • Make SNP key figures available. You define which SNP key figures PP/DS should use as safety stock or days’ supply. (Make SNP Key Figures Available)

    • Define planning area. You specify an SNP planning area that contains the key figures for the time-dependent safety stock/days’ supply levels. (Start of the navigation path Global Settings Next navigation step Maintain Global Parameters and Defaults) End of the navigation path

  3. Target stock level

    Choose a suitable target stock level method. In PP/DS you can use the following target stock level methods:

    • Target days’ supply from product master(’ ’)

    • Target stock level equals maximum stock level + safety stock (4)

      The target stock level is determined as follows: Target stock level = Maximum stock level + Safety stock

    • Maximum of maximum stock level/target days’ supply(5)

    • Sum of maximum stock level/target days’ supply (6)

    • No target stock level (7)

    Methods 1 to 3 are not supported in PP/DS.

Alert Monitor

The system can inform you by means of an alert that the safety stock or target stock level has been violated. This is only possible if you use safety stock methods SB, SM or MM or the target stock level method 4 (Target stock level equals maximum stock level + safety stock).

In the alert profile, on the PP/DS tab page under Inventory Alerts, you can select the following alerts:

  • Stock Fallen Below Safety Stock Level

  • Stock Fallen Below Target Stock Level

  • Stock Exceeds Target Stock Level

Note Note

To determine safety stock alerts, the system compares the current stock of a pegging area with the safety stock (static or dynamic) from the location-dependent product master. The system determines the time intervals in which the current stock falls below the safety stock level.

The current stock is the sum of the pegging-relevant receipts and issues (requirements) of a pegging area, minus the real and virtual safety stock requirements, which do not represent real requirements.

Up to and including SAP APO 4.0, there was no safety stock alert for the virtual safety stock method. In the real safety stock method, the safety stock alert is an undercoverage alert.

Because the real requirement element of the safety stock is missing in the virtual method, the system cannot determine a stock alert via the pegging relationship between receipt and requirement elements. Instead, it must compare the current stock with the target stock level.

End of the note.

For more information, see Monitoring PP/DS Alerts.

Business Add-In (BAdI)

You can use the Business Add-In /SAPAPO/RRP_SFTY_STK BAdI for Safety Stock Heuristic, to modify the heuristic SAP_PP_018, which generates safety stock requirements in the liveCache on the basis of the algorithm /SAPAPO/HEU_PLAN_SAFTY_STOCK.

Features

Safety Stock Methods

The following table explains the differences between the “real” and the "virtual" methods, and how they are both used.

Virtual Safety Stock Elements

Real Safety Stock Requirements

Use

To cover unexpectedly high requirements

To resolve delays or problems in production

Setting in planning version (Take Safety Stock Into Account)

Consider Virtual Safety Stock Elements (2)

Consider Safety Stock Requirements in SAP liveCache (3)

Effects on planning

The safety stock of a product is represented by virtual safety stock elements (safety stock requirements or receipts) that PP/DS only takes into account in the net requirements calculation, but that are not available as orders in the liveCache (that is, virtually). For this reason, dynamic pegging cannot take safety stock elements into account and create dynamic pegging relationships to them.

As of SAP APO 4.0, you can generate safety stock elements in the liveCache, using the heuristic SAP_PP_018. The safety stock of a location product is represented by an order in the liveCache. In the standard, it consists of a requirements element of the category SR. For this reason, the net requirements calculation in PP/DS and dynamic pegging both take this type of safety stock requirement into account.

Applications

Corresponds to the method in other APO applications, such as SNP and CTM.

These safety stock requirement elements are taken into account in PP planning heuristics, pegging, optimization, scheduling and the ATP check.

Safety stock methods

Static and dynamic safety stock

Static safety stock.

The dynamic method is not supported.

Pegging

Not relevant for pegging

Relevant for pegging

Consideration in planning

PP/DS procurement planning creates receipts (in a static safety stock method, for example) in order to cover a safety stock requirement for which there is insufficient stock. However, dynamic pegging is not able to create dynamic pegging relationships between the virtual safety stock requirement and the receipts that could cover it, leading to an “undercoverage situation”.

Before the planning run, the safety stock requirement causes an undercoverage situation.

During the planning run, a receipt element is generated to cover the safety stock requirement.

Use of the safety stock

This receipt element is available for real requirements that may occur at a later point in time.

This receipt element is usually assigned to the safety stock element and is not available for requirements that may occur at a later point in time.

Advantage

The safety stock influences the calculation of alerts and days' supply. The receipt element is visible as surplus because it generates an overcoverage situation and an overcoverage alert.

The safety stock influences the calculation of alert and days’ supply and is given order priority. In other words, a correct days’ supply calculation is carried out in the product view and the order priority can be used in optimization. You do not receive undercoverage alerts for covered safety stock orders; instead you receive undercoverage alerts for safety stock requirements that are not covered.

Disadvantage

Pegging, optimization, scheduling and ATP check do not take virtual safety stock elements that are not relevant for pegging into account. Because pegging is not available you must check the inventory alerts (Stock Fallen Below Safety Stock Level)

Real safety stock requirements can only be used with static safety stock methods. (Time-dependent methods are not supported.)

In dynamic pegging, the receipt element can first be assigned to the safety stock requirement, with the result that undercoverage alerts may occur for real requirements, for example, later sales orders.

As of SCM 4.1, you can use the heuristic SAP_PP_019 (Create Fixed Pegging Relationships) to ensure that order priority is taken into account when the system generates fixed pegging relationships.

Note Note

The system creates safety stock only in the make-to-stock segment. Only demands in this segment can consume safety stock.

End of the note.

Target Stock Level Method

The target stock level is a value for the available warehouse stock level that you want to reach through planning.

When planning with the standard heuristic Planning of Standard Lots (SAP_PP_002), the lot size depends on the target stock level.

Note Note

If you have chosen an exact lot sizing procedure and the safety stock method ’ ’ or 4-7 in the product master, then, in planning, the procurement proposals are created so that the safety stock level or the target days' supply is reached. With target stock method 4 (Target stock level = Maximum stock level + Safety stock) procurement is only carried out again if the stock level falls below the safety stock level.

End of the note.

If the current stock falls below the safety stock, a new procurement proposal is generated to fill the target stock level and cover the current requirement.

Inventory Alerts

For more information, see Monitoring PP/DS Alerts.

Constraints

  • To consider dynamic safety stock (such as safety days supply) in PP/DS, new alerts such as stock below safety stock, stock below target stock, and stock exceeds target stock are provided. Characteristics, shelf-life, and minimum and maximum pegging intervals are not considered for the new stock alert types.

  • The SAP ERP Customizing value for the percentage of safety stock availability is not integrated with SAP APO.

  • Product master data must be maintained within SAP APO to utilize the target stock level method functionality.

  • Time-dependent target stock level methods are not supported by PP/DS. Consequently, target stock alerts are only generated when a static target stock level method is used.

  • The fill level of the container resource is not affected. For planning, PP/DS does not take all possible values into account that can be maintained on the Lot Size tab page in the APO Product Master - in contrast to SNP planning.

Example

During planning with the standard heuristic SAP_PP_002 and the target stock level method 4 (Target stock level = Maximum stock level + Safety stock) procurement proposals are only created again if the stock falls below the safety stock level.

More Information

Safety Stock Planning in Supply Network Planning

Safety Stock Planning

Safety Stock Planning in Production Planning and Detailed Scheduling (PP/DS)

Heuristics for Production Planning

Pegging Relevance of Safety Stock

Product Availability Check with Safety Stock