With both an Order Management System (OMS) and a Warehouse Management System (WMS), we have two stages of allocation: Order Allocation -> which creates Shipping Orders/Shipments from Orders; and Shipment Allocation -> which creates Shipping Containers from Shipments and allocates specific units of inventory to a given Shipment and Shipping Container.

Order Management just needs to know there are available qualifying units for a given item in order to allocate and create a shipment for that item. And the OMS won’t allocate more than is available to ship. Units available for allocation, however, is not necessarily a straight forward answer. We’ll get into the dimensions of this question in another post.

Having established, however, that there are sufficient units of inventory for a given order, the resulting shipment must also pass through an allocation step in WMS. The Shipment Allocation assigns specific units in specific locations to a given Shipping Container. The Shipment Waving process allocates these units to a Shipping Container setting which Units in which Locations in which IUM configurations are going to be picked and shipped in a given Shipping Container.

In contrast to the OMS allocation, the specificity of the WMS allocation is vital. While the OMS just needed to know that there was sufficient inventory, the WMS assigned (and will decrement) units of inventory from specific locations. If the picker on the floor disregards the Work Instructions from the WMS, your location inventory figures will be in disarray, even if the summary figures back up to OMS still hold true.