Consideration of Material Constraints

In Production Scheduling, the On-Hand Inventory table shows an item's shortage quantity, in addition to on-hand, reserved, and on-hold quantities.

For all items in the production schedule, existing supplies (on-hand, inbound transfer order, purchase order, and work order) and existing demands (sales order, outbound transfer order, and work order component demand) are considered.

• If total demand for an item exceeds total supply for an item, then a shortage quantity will be reported in the On-Hand Inventory table for that item. Work order operations that consume shortage quantity are scheduled after the Shortage Resolution On date, which is set to horizon start + item's lead time. The date Earliest Shortage Usage displays the start of the earliest operation that consumes this shortage quantity.
• If the total supply exceeds the total demand for an item, then there's no shortage. If inbound supplies, such as purchase orders, arrive later than the consuming work orders require based on their need-by date, the work orders are delayed and scheduled to start after the supplies become available.

A work order can be late for various reasons. For example, sub-assemblies can't be completed early enough, inbound supply issues, resource capacity and availability constraints, or a combination of these. If a work order is scheduled late, and capacity constraints don't explain the lateness (you see idle time on the relevant resources), then you can use the schedule analysis capabilities in the Gantt chart and the tabular schedule views to get more insights. To do this:

• Select the operation and activate Show Pegging Links to see which upstream processes it depends on and possibly must wait for. Only pegging links to work order operations that are currently displayed in the Gantt chart are displayed.
• Use Highlight Pegged to shortage in the Gantt toolbar, that will highlight all operations that are pegged to a shortage quantity as defined above.
• Select one of these highlighted operations in the Gantt chart. Navigate to the On-Hand Inventory table, and toggle on Filter by Gantt Selection above the table. The table shows only those items that are consumed by that operation, and in this case at least one of them will have a shortage quantity. Then evaluate the item's lead time and compare the dates Shortage Resolution On and Earliest Shortage Usage and see whether this explains the lateness. For evaluation of the scenario, you can override the lead time and run another solve.
• If there's no shortage shown, then switch to the Inbound Supplies tab and do the same. Select operation of interest in the Gantt chart and toggle on Filter by Gantt Selection above the table. Only those inbound supplies that are pegged to the selected operation will be shown. Evaluate their Requested Date and see whether this explains the lateness. For evaluation of the scenario, you can override the requested date and/or add new supplies, none of which will be released to SCM Execution.