What is a WMS?
A WMS (Warehouse Management System) is software that directs and records every physical process in a warehouse or distribution centre, from receiving and putaway to order picking, stock counting and dispatch, at the level of individual locations, pallets, batches and serial numbers. Where the ERP knows how much stock a company owns financially, the WMS knows exactly where each unit is and which operator, forklift or robot should move it next. In manufacturing, the WMS is therefore a link between business planning, MES and automation on the shop floor. It is a specialised management system for one domain: the warehouse.
A WMS provides real-time insight, control and efficiency in warehouse logistics.
🎯 What does a WMS do?
A WMS tracks every goods movement through scans and directs staff with concrete instructions (tasks) instead of paper lists.
| Function | What the WMS does |
|---|---|
| Receiving (inbound) | Checks the delivery against the purchase order or despatch advice, records batch numbers and best-before dates (THT), prints labels |
| Putaway | Selects the best storage location using rules: product group, weight, temperature, turnover rate |
| Inventory Management | Tracks quantities per location, pallet, lot and serial number, including blocks and quarantine |
| Replenishment | Automatically refills pick faces from bulk storage |
| Order picking | Sends pick tasks to handheld scanners, voice picking, pick-to-light or goods-to-person systems |
| Dispatch (outbound) | Checks, packs, prints SSCC labels and passes data to the TMS |
| Cycle counting | Counts locations continuously instead of one annual stocktake |
| Traceability | Records which batch went to which customer, using GS1 codes or, in healthcare, HIBC barcodes |
🔧 How does a WMS direct the warehouse?
The strength of a WMS lies in its rules. Three choices determine how efficient a warehouse is:
- Issue strategy - FIFO (first in, first out) for ordinary goods, FEFO (first expired, first out) for products with a shelf life, and occasionally LIFO. For food and medicines FEFO is usually the norm.
- Picking method - order picking (one order per trip), batch picking (several orders at once), zone picking (each operator works their own zone) or wave picking (orders released in waves matched to truck departure times).
- Slotting - fast movers close to dispatch and at grab height, slow movers at the back. An ABC analysis of turnover rate is the starting point.
Identification relies on barcodes and increasingly RFID. At pallet level, the SSCC (18 digits) on a GS1-128 logistic label is the standard. The supplier sends the same number in advance in an EDI message (DESADV), so the WMS needs just one scan per pallet on receipt.
🏭 How does a WMS work with OT and automation?
In a manual warehouse, the WMS only talks to people and scanners. Once automation is added, a layered architecture emerges that maps closely to the Purdue Model and ISA-95:
| Layer | System | Task | Typical time scale |
|---|---|---|---|
| Level 4 | ERP | Orders, purchasing, financial stock, master data | Hours to days |
| Level 3 | WMS | Locations, tasks, picking, traceability | Minutes |
| Levels 2–3 | WES / WCS | Sequencing and routing of conveyors, sorters, shuttles | Seconds |
| Levels 1–2 | PLC and SCADA | Motors, sensors, safety, visualisation of the installation | Milliseconds |
| Floor | AGVs and AMRs | Physical transport, directed by a fleet manager | Continuous |
The WCS (Warehouse Control System) translates WMS instructions into signals for the controllers of conveyors and sorters. A WES (Warehouse Execution System) combines that control with parts of the WMS functionality, such as releasing order waves. The boundaries between these systems are blurring. ISA-95 classifies these activities as inventory operations management, one of the four level 3 categories alongside production, maintenance and quality.
In manufacturing, the WMS supplies raw materials to the line and receives finished goods. An example: a
pallet with batch number L240725A leaves the filling line. The MES reports the production as
complete, the stretch wrapper’s PLC sends a signal, the WMS assigns an SSCC and an AGV takes the pallet to
a location chosen by the WMS. On dispatch, the WMS applies FEFO and picks the batch with the earliest
best-before date.
🔄 What is the difference between WMS, ERP, MES and TMS?
| System | Focus | Stock detail level | Role relative to WMS |
|---|---|---|---|
| WMS | Physical warehouse processes | Location, pallet, batch, serial number | Executes the stock movements |
| ERP | Company-wide: orders, finance, purchasing | Item per warehouse | Sends orders, books value and receives confirmations |
| MES | Production process and traceability | Consumption per production order | Requests material and reports finished goods |
| TMS | Transport planning and carriers | Shipment and route | Receives shipping data and loading sequence |
Many ERP packages include their own warehouse module. That is sufficient for simple warehouses. With high volumes, many locations, automation or strict traceability requirements, companies usually choose a separate WMS or an extended module such as SAP Extended Warehouse Management (EWM).
📦 Which WMS solutions are available?
- Open source - Odoo Inventory, ERPNext, OpenWMS
- Commercial - SAP EWM, Oracle WMS Cloud, Manhattan Associates, Blue Yonder, Körber
- Focused on manufacturing and automation - Rockwell Plex (part of Rockwell Automation), SSI Schäfer WAMAS and the software of other warehouse automation suppliers
More and more WMS packages are delivered as a cloud service (SaaS). That reduces the management burden but makes the warehouse dependent on internet connectivity and the vendor.
📊 How do you measure WMS performance?
A WMS provides the data for the most important warehouse KPIs. Many organisations use these indicative targets:
| KPI | What it measures | Indicative target |
|---|---|---|
| Inventory accuracy | System stock matches physical stock per location | 99% or higher |
| Picking accuracy | Order lines picked without error | 99.5–99.9% |
| Dock-to-stock | Time from receipt to available stock | Within 24 hours, often a few hours |
| Order cycle time | Time from order release to dispatch | Depends on the cut-off, often same day |
| Picks per hour | Productivity per operator | Strongly dependent on picking method and item |
Treat these values as a starting point. What is achievable depends on the product range, the level of automation and the quality of master data.
🔐 How do you secure a WMS?
A WMS is business-critical: if it fails, dispatch stops and often production too. NotPetya demonstrated this in June 2017. At Maersk, container terminals, including those on the Maasvlakte in Rotterdam, were at a standstill for more than a week because the IT systems for planning and logistics had been destroyed. Key measures:
- Segmentation - separate warehouse automation (WCS, PLCs, AGVs) from the office network using network segmentation and the zones and conduits model from IEC 62443.
- Mobile devices - handheld scanners on Wi-Fi are endpoints with access to the WMS. Use WPA2/WPA3-Enterprise and device management, and replace legacy Windows CE terminals.
- Interfaces - secure APIs and EDI connections with customers, carriers and suppliers, and assess the vendor of a cloud WMS as part of supplier security.
- Continuity - test recovery and keep a fallback procedure on paper or with locally printed labels ready; see business continuity. Ransomware increasingly targets logistics.
For organisations covered by the Dutch Cybersecurity Act, the national implementation of NIS2 in force since 15 August 2026, the WMS falls within the duty of care. This applies, for example, to companies in transport and in food production and distribution.
🧭 How do you implement a WMS step by step?
- Map processes and volumes - orders per day, lines per order, number of items and locations, peak periods.
- Define traceability requirements - think of HACCP in the food industry, and GMP and the EU guidelines on good distribution practice for medicines.
- Clean up master data - dimensions, weights, packaging units and GTINs must be correct, otherwise slotting does not work.
- Design locations and labels - a logical location coding scheme and scannable labels on every rack.
- Define interfaces - ERP, MES, TMS and possibly WCS, with agreements on messages and error handling.
- Test with real orders - including peak loads, failures and a fallback scenario.
- Go live in phases - start with one zone or one customer, then expand.
❓ Frequently asked questions
What does WMS stand for?
WMS stands for Warehouse Management System. A WMS directs receiving, storage, picking, stock counting and dispatch, and records every goods movement at location level.
Do I need a WMS if I already have an ERP?
An ERP system usually manages stock per item and per warehouse, not per rack location or pallet. For a small, straightforward warehouse, the ERP’s warehouse module is often enough. With high volumes, automation or strict batch traceability, a separate WMS delivers more accuracy and speed.
What is the difference between a WMS and a WCS?
A WMS decides what needs to happen: which order, which location, which batch. A WCS (Warehouse Control System) determines how the automation carries it out and drives conveyors, sorters and shuttles via PLCs. A WES sits in between and partly combines both roles.
What is the difference between FIFO and FEFO in a WMS?
With FIFO, a WMS issues the stock that was received first. With FEFO, the WMS selects the batch with the earliest expiry date, regardless of when it arrived. FEFO is standard practice for food and medicines.
Can a WMS control AGVs and robots?
A WMS issues transport orders but usually does not control AGVs and AMRs directly. A fleet manager or WCS does that, distributing the WMS orders across vehicles and planning the routes. The WMS then receives confirmation that the pallet is at its new location.
Does a WMS fall under NIS2 or the Dutch Cybersecurity Act?
A WMS is not a regulated product in itself, but it falls within the duty of care of an organisation covered by NIS2 or the Dutch Cybersecurity Act. That means risk analysis, access management, supplier security and a continuity plan, even when the WMS is consumed as a cloud service.
📌 In summary
A WMS digitises and optimises all warehouse processes down to location, batch and serial number level. It is the link between ERP, MES, inventory management and floor automation, supports traceability with GS1 standards and is so business-critical that security and continuity must be built in from the design stage.