Picking Strategies - SAP WM

The strategies that are used in WM to remove goods from storage are listed in the following table.

Picking-Strategies

To access the objects (tables or views of tables) for the stock removal search strategies, see the corresponding section under Strategies in the WM Implementation Guide.

Transfers Out of the Warehouse
The system gets the information for the source and destination storage bins when goods are picked and transferred out of the warehouse as illustrated below.

Transfers Out of the Warehouse

Information for Stock Removal
When stock is removed from the warehouse, it generally is transferred to the interim goods issue storage area. This information about the destination (interim storage type, interim storage section, and interim storage bin) is recorded in the transfer requirement or the system determines it from the WM movement type.

Storage Type Search
The system must now determine from which storage type the material should be picked. You define this information in the storage type search table. To make entries in this table, see the section on defining the storage type search sequence under Strategies in the Warehouse Management IMG documentation.

In the storage type search table, you can define a search sequence with up to ten storage types. (Be sure to enter an A for stock removal in the Act. column.) The list of storage types is hierarchical, that is, the system searches for the material in the first storage type, then in the second storage type, and so on. An entry of *** for the storage type means that the system searches throughout the entire warehouse for the oldest stock. The table entry that the system uses for this search depends on the material being removed from storage.

You can group materials together by a storage type indicator so that the system uses the same search sequence and removes materials from the same storage type or types. To implement this you define a:

  • Storage type in the material master record (the Stock removal field)
  • Storage type indicator in the storage type search table (in the TyInd field)

Storage Bin Search
Once the storage type has been determined, the system then searches within the storage type to find an appropriate storage bin from which the material can be removed. To find a storage bin, the system uses a search strategy that has been defined for the storage type. For each storage type you can define one picking strategy.

Customer-defined Strategy
To use customer-defined strategies, you must select the User exit active field in the Stock Removal Control section of the appropriate storage type record. For instructions, see the section on Developing function extensions in the Warehouse Management IMG documentation.

Strategy F: FIFO (First In, First Out)
Use
With this picking strategy the system proposes the oldest quant in the storage type as the quant that should be transferred. The system generally calculates the "age" (length of time in storage) of a quant on the basis of the goods receipt posting date from the Inventory Management (IM) application component. The system automatically sets the goods receipt date in the quant and in the transfer requirement for every goods receipt posting in IM. When the transfer order is created, this date is copied over to the quant record of the destination storage bin.

You can accept the goods receipt date that the system sets or you can enter a different date. Regardless of whether the system proposes the goods receipt date or you enter a different date, the date is used to calculate the age of the quant. This date influences the sorting sequence for each material.

Prerequisites
When you define the storage type record to use this strategy, enter f in the Picking strategy field.

Strategy: Stringent FIFO Across All Storage Types
Explanation of the Strategy
It is generally assumed that only one picking strategy is allocated to each storage type. However, a strategy based on the storage type is not usable in all sectors of industry.

In WM, it is possible to pick stock according to the FIFO principle by taking into account all quants within a warehouse. In this case, the system does not scan individual storage types in sequence but it proposes the oldest quant in the entire warehouse as the quant to be removed from the warehouse. The system does not take into account the picking strategies specified for the individual storage types. This would lead to inconsistencies.

Some storage types should be excluded from the stringent FIFO strategy, otherwise incorrect picks would result. For example, the interim storage area for differences should be excluded from the stringent FIFO strategy. The stringent FIFO strategy is set or switched off in the table Exclusion of storage types from Stringent FIFO .

Setting up the Strategy
In the Storage Type Search table enter three asterisks ( *** ) in the first Storage type column as illustrated below.

Setting up the Strategy

When you create pick transfer orders, you can also enter *** in the field for the source storage type in the transfer order preparation screen or in the transfer order item screen.

  • It is necessary to exclude some storage types, such as the interim storage area for differences, from the stringent FIFO strategy. In the table Exclusion of storage types from Stringent FIFO select the No stringent FIFO column for the storage type. The system then ensures that this storage type is not used for the stringent FIFO picking strategy. This indicator should be set for allinterim storage types.

Strategy L: LIFO (Last In First Out)
Use
For some warehouse organizations or sectors of industry, the FIFO principle cannot be used. For example, in the building material industry material that is being stored temporarily, that is, material that is going to be transferred immediately out of the warehouse, is stacked on material that is already in the warehouse. If the FIFO strategy is used during picking, the material lying on top must be moved so that the warehouse worker can reach the material with the oldest goods receipt date. The LIFO strategy is provided for such situations. When the system searches for a quant to remove from stock, it always selects the last quant that was placed into stock.

Prerequisites
When you define the storage type record to use this strategy, enter L in the Picking strategy field.

Strategy A: Partial Quantities First
Use
With this picking strategy the FIFO principle is overridden in order to optimize the management of stock in the warehouse. The number of storage units with partial quantities in the storage type is reduced to as few as possible. This strategy is appropriate only when standard storage unit types are used for stock placement (the same quantity of a material for a specific storage unit type)

  • partial storage unit quantities are less than the standard storage unit quantities
    Within a storage type there are two different types of quants:
  • quant in an amount that is normally contained on the standard storage unit, according to the storage unit type defined in the material master record
  • quant in an amount that is smaller than the standard storage unit. This is known as a partial storage unit quantity. A quant that is larger than a standard storage unit should not occur.

When the system searches for a quant, it follows these steps:

  1. If the required quantity in the transfer order is the same or greater than the quantity of a standard storage unit, the system attempts to remove a standard storage unit from stock.
  2. If no standard storage units are available, partial storage unit quantities are used.
  3. If the required quantity in the transfer order is less than the quantity of the standard storage unit, the system first tries to remove partial storage unit quantities from the stock.
  4. If no partial storage unit quantities are available, full storage units are broken. The search for full storage units is carried out according to the FIFO principle.

Prerequisites
When you define the storage type record to use this strategy, enter a in the Picking Strategy field.
When you create the warehouse data view for the material master record, you must define the specifications for the standard storage unit.

Strategy M: According to Quantity
Use
This picking strategy is based on whether the quantity required in the transfer order is large or small. You can have a storage type in which small quantities of material are stored (generally a storage type with a fixed storage bin organization). There can also be a reserve storage in which larger quantities are stored.

The system decides whether it is dealing with a "small quantity" or a "large quantity", depending on the quantity required in the transfer order. The storage bin that the system proposes for the pick is either from the small quantity storage type or large quantity storage type. As the criterion for this quantity check, the system uses the control quantity defined in the Control quantity field in the material master record. The system can suggest a stock removal quantity for the picking technique “according to quantity” as well as for “random picking”.

Handling Small and Large Quantities
This illustrates how WM handles small and large quantities.

WM handles small and large quantities.

In the example above, two storage types are used to fill delivery notes from the Sales and Distribution system:

  • Fixed bin storage
  • High rack storage

The system selects the quant from a storage bin in fixed bin storage if the required quantity is less than or equal to the control quantity defined in the material master record. If the required quantity is larger than the control quantity, the system searches for the quant in high rack storage.

Prerequisites
To use this strategy,

  • Enter m in the Picking strategy field of the storage type record.
  • When you maintain the entries in the Storage Type Search table, for the first storage type you must enter the storage type for the smallest quantity; for the second storage type in the sequence you enter the storage type for the medium size quantity, and so on.
  • When you create the warehouse data view of the material master record, you must enter a quantity for the small quantity storage type in the Control quantity field. The system uses this quantity to determine whether the required quantity should be removed from the small quantity storage type or from another storage type.

For this strategy, the standard system uses movement type 603 to determine which storage type is used for small stock removals for deliveries.

Example: Rounding Off Requested Quantities
When you process the picking strategy, you can round off the requested quantity in the transfer order item. In Customizing, you can switch this on in the storage type record in the Stock removal control section. You define the rounding quantity itself in the material data for the storage type.

Quantity rounding is advantageous in combination with picking strategy “M“. For example, if pallet quantities, carton quantities or individual quantities are to be picked from a chain of three storage types, this can be attained by defining the rounding quantity and control quantity in the material master record as follows:
For the first storage type in the storage type search sequence (removal of a single piece) you enter the number of pieces in a carton minus one as the control quantity. You do not need to maintain the rounding quantity since this does not have to be rounded. For requested quantities that are greater or equal to a carton, the system will then skip over this storage type.

For the second storage type in the search sequence (removal of complete cartons) you enter the pallet quantity minus one as the control quantity in the material record. The rounding quantity is the carton quantity. For requested quantities that are greater than or equal to one pallet, the system skips this storage type. The system only generates transfer order items for complete cartons. For the remaining quantity (individual pieces) the system reenters the storage type search sequence and picks these from the first storage type.

You do not need to enter a control quantity in the material master for the third storage type in the search sequence (removal of complete pallets). The rounding quantity is the pallet quantity. The system only generates transfer order items for full pallets. For the remaining quantity, the system returns to the storage type sequence and picks from the first or second storage type.

For this logic, you should be aware of the two following points:

  • The system does not round to zero. This means that if there are not enough individual pieces in the first storage type, a carton in the second storage type will be broken open.
  • If the requested quantity is larger than the available quantity in a storage bin, it is not rounded. In other words, if a carton plus a few individual pieces are located in a bin in the second storage type and the requested quantity is larger, the bin will be emptied.

Strategy H: Shelf Life Expiration Date
Use
With this picking strategy, the system ensures that materials with the oldest expiration date will be removed from stock first.

Prerequisites
To set up the system to manage materials with a shelf life expiration date (SLED), you need to carry out the following tasks:

  • Activate shelf life expiration date management in the Control Data section of the warehouse number record.
  • Activate picking strategy h in the storage type records concerned.
  • Maintain the data in the Storage view of the material master record.

Color Codes in the SLED Control List

Color Codes in the SLED Control List

You should use this report as a batch request for larger quantities of stock.

Strategy P: Fixed Storage Bin
Use
In this picking strategy, the system uses the storage bin that was entered in the material master to find stock. We recommend that you set up replenishment control for the fixed storage bin when you use this strategy.

Prerequisites
A fixed storage bin must be assigned to the affected materials in the material master.

Stock Return Methods
Purpose
When stock is picked from a storage type for which the "complete stock pick" has been defined, sometimes small quantities are left over after the required quantity is picked. The remaining quantity is returned to a storage bin via a "return" sub-item in the transfer order.

With the Warehouse Management (WM) component, you have three methods at your disposal for returning quantities to a storage bin.

  • The stock remains at the destination bin, that is, the storage bin to which it is transferred.
    The remaining quantity remains in the picking area.
  • The stock is returned to the source bin, that is, the storage bin in which it was originally stored.
    The remaining quantity is returned to the high rack storage area where the original quantity was stored.
  • The stock is transferred to another storage bin (warehouse for partial quantities).
    If the stock is returned to another storage bin, the system uses the putaway strategy specified for this storage type. You can change the default that the system proposes for the return storage bin in the transfer order.

Prerequisites
Regardless of the method used, you must also set the Complete Stock Pick Active indicator in the Pick Control section of the storage type record.

The return method described here is not valid for SU-managed storage types. If you are implementing the complete stock pick for SU-managed warehouses, only the variants “complete stock pick with return to the same storage bin” or “complete stock pick using a pick point” are possible. Departures from this rule are only possible by using a customer exit.

Process Flow
When the system searches for a storage bin for the return quantity, it uses the following hierarchy.

  1. The overdelivery quantity can be kept in the storage bin to which it was transferred, that is, the destination storage bin in the transfer order. You must set the Retain overdeliveries indicator in the Putaway Control section of the storage type record for the destination storage type.
  2. The return quantity is returned to the storage bin from which it was transferred, that is, the source storage bin in the transfer order.
  3. You must set the Return stock to same storage bin indicator in the Stock Pick Control section of the storage type record for the source storage type.

  4. The return quantity is transferred to the storage type and bin according to the movement type. In the movement type record, you must define the return storage type and the return storage bin.
  5. The return quantity is transferred to a storage type defined in the storage type record.
    You must enter a storage type in the Return storage type field in the Pick Control section of the storage type record for the source storage type.
  6. The return quantity mustbe kept in the storage bin to which it was transferred, that is, the destination storage bin in the transfer order.

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