A warehouse management system (WMS, German Lagerverwaltungssystem, LVS) is software for controlling and administering the processes in a warehouse — from goods receipt through put-away, replenishment and picking to dispatch. It keeps stock at storage-location level and directs the work orders of staff and of the connected equipment.
Tasks
Core functions include storage location administration and location strategies, goods receipt handling with quality inspection, replenishment control, pick guidance, packing and dispatch handling, stocktaking procedures and the administration of batches, serial numbers and best-before dates. Through material flow controller functions or through interfaces, the system directs automated equipment such as storage and retrieval machines, shuttle systems and automated guided vehicles.
Demarcation from the ERP warehouse module
ERP systems as a rule keep stock at plant or storage-location level and map simple warehouse processes. A warehouse management system works at storage-bin and load-unit level, optimises routes and sequences, and controls equipment in real time. The boundary is fluid: systems such as SAP EWM are functionally complete warehouse management systems inside an ERP landscape.
Interfaces according to VDI 3969
Warehouse projects fail at the interfaces more often than at the technology. VDI 3969 describes them for the connection between the warehouse management system and the higher-level system — that is, to merchandise and materials management, to sales or to production planning. The guideline distinguishes six logical interfaces:
- Expected receipt — only goods already expected and known in the upstream system, for instance from purchase order administration, should be announced to the warehouse management system as an incoming receipt.
- Receipt confirmation — the report of what actually arrived.
- Retrieval order — covering retrieval and picking. An order carries one or more lines that refer to articles or to other identities assigned at receipt. These orders are generated in the higher-level system.
- Order execution report — the report of what was actually provided.
- Goods data changes — corrections to stock and to the properties of goods.
- Master data — the shared data basis of both systems.
One demarcation in the guideline matters for requirement specifications: it treats the interface upwards. Material flow controllers for automated conveying equipment, forklift control systems, route optimisation and picking systems it names as subsystems and neighbouring systems whose interfaces it expressly does not treat in detail. Whoever writes a requirement specification therefore finds the connection to the ERP set out here — the connection to the equipment has to be specified by the author.
The guideline draws the scope of the warehouse management system itself from the goods receipt ramp to order-conforming provision at the dispatch ramp: goods receipt handling with quality control, put-away including repacking and the identification point, warehouse administration per storage location, internal replenishment and retrieval.
Selection and rollout
Choosing a warehouse management system is less a software decision than a process decision: the location strategy, the picking method and the replenishment logic have to be defined before they can be mapped in a system. The customary route runs through process capture, requirement specification, tender and trial operation — the structure of such a specification is set out in writing a WMS requirement specification. In practice, introducing a warehouse management system is considered together with warehouse planning, because layout, equipment and system logic depend on one another.
Source
VDI 3969 "Interfaces of the warehouse management system to higher-level systems", sections 1 and 2.
Warehouse management system in practice: Our services overview brings together the relevant planning and consulting approaches.