Warehouse (WM / EWM)

Inventory management in MM knows how much stock sits in a plant and storage location. Warehouse management knows exactly where: which bin, on which rack, in which zone. SAP models a warehouse as a hierarchy: a warehouse number contains storage types (shelving, pallet racking, a goods receipt area), which contain storage bins. Each bin holds quants, quantities of a material.

Classic WM moves goods with two documents:

• A transfer requirement is the to-do: “these goods need to move.” It’s created automatically, for example by a goods receipt.
• A transfer order is the instruction: “move 50 units from the goods receipt area to bin STBN-1-077.” Putaway and picking strategies, such as fixed bin, next empty bin or FIFO, propose the bins.

The main flows:

Flow	Steps	T-codes
Inbound	Goods receipt (MIGO) puts stock in an interim GR area → transfer requirement → putaway transfer order → confirm	MIGO, LB10, LT04, LT12
Outbound	Outbound delivery → picking transfer order → confirm pick → post goods issue (601)	VL01N, LT03, LT12, VL02N
Internal	Stock moves between bins, stock transport between plants, physical inventory counts	LT10, ME21N (UB), LX16, LI11N, LI20

Confirmation is the key moment: until a transfer order is confirmed, usually by scanning, the system doesn’t trust that goods are in the new bin.

EWM (Extended Warehouse Management) is SAP’s more powerful successor, now standard in S/4HANA. The ideas carry over with new names: warehouse requests instead of transfer requirements, warehouse tasks instead of transfer orders, plus features like slotting, wave management and labour management.

Strategies that choose the bin

Putaway strategies decide where incoming stock goes, for example:

• Fixed bin: each material has its own bin (common for picking areas).
• Next empty bin: the first free bin in sequence (common for pallet racking).
• Addition to existing stock: put the new quantity where the material already is.
• Open storage: one bin per storage section, for bulky goods.

Picking strategies decide where to take stock from:

• FIFO: the oldest quant first.
• Shelf-life expiration date: the earliest expiry first, for food and pharmaceuticals.
• Fixed bin: pick from the material’s fixed bin.

A storage type search sequence tells the system which storage types to try, in order.

Interim storage types

Goods between inventory management and a bin sit in interim storage types: 902 is the goods receipt area, 916 the shipping area for outbound deliveries, and 999 holds differences found in counts. Quants in interim types are normal for minutes or hours; quants that stay there for days are a sign that transfer orders weren’t created or confirmed.

Inbound:

1. MIGO posts the goods receipt (movement type 101); 50 units appear in interim type 902 and a transfer requirement is created.
2. LT04 creates a transfer order from the requirement; the putaway strategy proposes bin STBN-1-077.
3. The warehouse moves the goods and confirms the transfer order (LT12). Only now does the system show the stock in the bin.

Outbound:

1. VL01N creates the outbound delivery.
2. LT03 creates a picking transfer order; the picking strategy proposes the bin.
3. The picker confirms (LT12), and the goods move to the shipping area.
4. VL02N posts goods issue (movement type 601).

Counting and differences

Physical inventory in WM can run as an annual count or continuously during the year (LX16 for continuous inventory). Counts are entered (LI11N); differences are moved to interim type 999 (LI21) and then posted in inventory management (LI20), which creates the accounting entry for the gain or loss.

EWM’s building blocks

• Warehouse requests: the incoming or outgoing need, created from deliveries.
• Warehouse tasks: the individual moves (successors to transfer orders), grouped into warehouse orders for a worker or resource.
• Handling units: pallets or cartons tracked as units with their contents.
• Storage control: process-oriented (steps such as unloading, quality check, deconsolidation, putaway) and layout-oriented (moving through intermediate points such as conveyors).
• Waves: groups of picks released together to meet carrier departure times.
• Further functions: slotting, labour management, yard management, cross-docking, value-added services and kitting.

Embedded or decentralized

Embedded EWM runs inside S/4HANA, sharing master data and avoiding interfaces, and suits most warehouses. Decentralized EWM runs on a separate system, which can make sense for very large, highly automated warehouses that must keep running even when the central ERP is down. SAP distinguishes basic and advanced EWM functions, with the advanced ones (such as labour management, slotting and material flow control) licensed separately.

The end of classic WM

Classic WM (LE-WM) is not the target architecture in S/4HANA. It was available only under a compatibility arrangement that ended in 2025, so companies moving to S/4HANA migrate warehouses to EWM or, for simple storerooms, to lighter options such as stock room management. Understanding WM still helps: many concepts and many interview questions carry over directly.

Automation and radio frequency

EWM’s RF framework drives handheld scanners for every step, and its material flow system connects to conveyors, sorters and automated storage, sending them tasks and receiving confirmations. In highly automated sites, most moves are confirmed by machines rather than people.

When stock isn’t where the system says

• Stuck in interim areas: tasks not created or not confirmed. Check open tasks and interim quants.
• IM and WM disagree: a difference was cleared on one side but not the other, or a movement bypassed the warehouse.
• Bin blocked: a block for counting or putaway prevents picking.
• Handling-unit mismatches: a pallet’s recorded contents don’t match reality after an unrecorded repack.