The announced end of maintenance of SAP Warehouse Management at the end of 2025 in S/4HANA puts many users under pressure to make a timely decision: Introduce Stock Room Management or rather rely on SAP Extended Warehouse Management as a warehouse management system? Those who have been well served with WM up to now and do not expect any serious process changes in the future often opt for Stock Room Management. The decision is obvious: The functionalities are the same and can be operated as usual. If it weren't for the functions that are no longer available in Stock Room Management, but are needed for the company's own warehouse management. An important topic here is the warehouse control computer: the current interfaces to the automated warehouse can no longer be used from 2026. We show you possible scenarios for the interface replacement of automated warehouses that are already in use or are to be newly connected.
WM-LSR interface: one-way and two-way communication path
The same interface is used for communication between the WM system and a warehouse lift or automatic warehouse: WM-LSR. Through this interface, with the help of a function module, an intermedia document - IDoc for short - of type WMTORD is sent, which is understood by the lift or automated warehouse as a picking order. A WMTORD IDoc contains information about the material to be picked, the quantity and the storage bin where the item is located.
Although the interface is the same, it can be different. The interface to the warehouse lift is a simple interface with a one-way communication path. This means that the system sends only one IDoc - the picking order - and does not receive any feedback. The feedback about picking takes place in the form of an acknowledgement of the order not via the LSR interface, but elsewhere.
The LSR interface to an automated warehouse is usually much more complex: Here, not only is a picking order sent via IDoc, but a response is also received in the form of an inbound IDoc. This is why we are talking about a two-way communication path here. Furthermore, this type of interface uses several IDoc types that contain, for example, a cancellation request or confirmation.
Replace interface to the warehouse lift
Companies that want to connect a warehouse lift in their warehouse and operate it via the WM-LSR interface should take the future conversion to Stock Room Management or EWM into account during implementation: Regardless of the future system, the conversion to S/4HANA will result in renewed effort for the interface connection. In order to avoid duplicate effort, the following solution is recommended right from the new connection of the warehouse lift in the WM system: a replication of the IDoc type /SCWM/WMTORD in the Z namespace. Although this IDoc type is an EWM IDoc type, it can be mapped in the Z namespace. This has the advantage that the interface remains intact and can continue to be used even after the conversion to Stock Room Management. If the company switches to EWM in the future, the standard EWM-LSR interface with the mapped IDoc type and the standard function module can be used there.
For companies that already have an elevator in use and operate it via the WM-LSR interface, there is also a timely mapping of the IDoc in the Z namespace if the Stock Room Management is to be the future system: depending on the actual S/4HANA strategy, either before the changeover or during it. This relieves the project team during the changeover phase. If the company switches to SAP EWM before January 1, 2026, this issue is not applicable, since the standard interface can be used in EWM.
Replace interface to automatic warehouse
In principle, the same considerations apply to communication with the automated warehouse that are used to replace the interface with a simple communication direction. However, due to the complexity of the interface characteristics, an individual consideration of the existing solution is required here: Depending on the process complexity, further solution paths such as replication of the WM IDoc types in the Z namespace and others can be considered. Company-specific process and organizational characteristics should also be taken into account in the decision-making process. So, here it is necessary to consider the benefits and challenges of the options in order to make the right strategic decision.
Due to the complexity of the interface to the automated warehouse, the existing solution should be examined more closely when replacing it. Company-specific process and organizational characteristics should also be taken into account in the decision-making process. It is therefore an individual decision in which we will be happy to support you.
