What causes the exception message "Reschedule In Operation" at the end of the MRP run?

The exception message "Reschedule In Operation" occurs when the requirements date for a planned order falls before the date of a firmed planned receipt. In the context of Material Requirements Planning (MRP), firmed planned receipts are orders that are confirmed and cannot be easily altered. If a requirement is set to occur earlier than the availability of the firmed planned receipt, the system recognizes a conflict in scheduling and triggers this exception to signal that the planning needs to be adjusted.

This situation commonly arises in scenarios where demand changes, and existing planned receipts do not align with newly scheduled requirements. The MRP system identifies that there is a discrepancy and requires a revision of the plan to ensure that materials are available when needed, without violating the constraints set forth by firmed orders. Therefore, the focus is on ensuring that material availability aligns with the timing of requirements, which justifies why the message indicates a need for rescheduling in operation.