APS Processing of Plan Materials at Operation Start

If a job or production schedule is released but NOT scheduled, APS plans the materials based on the setting of the Plan Materials at Operation Start field, in this order:

When APS generates a PLN to satisfy a demand, it always plans the PLN's materials to be due at the start of the operation.
If you then firm the PLN into a job or production schedule and rerun APS Planning, it again plans the materials at the start of the operation.
Finally, when you release the job or production schedule and rerun APS Planning, the Plan Materials at Operation Start parameter determines whether the system plans the materials at the start of the operation or at the start of the job.

Note:

If this parameter is cleared, the material demands will be due earlier than they were due in previous runs of APS Planning, before the job/production schedule was released. If you are running in APS mode, this situation may cause problems with resource capacity. Select this parameter to avoid this issue.
Items for which the MRP Item is selected are not affected by this parameter; they always require materials at the job/PS release start date.
Planned orders (PLNs) are not affected by this parameter; required materials for a planned order are always planned at the start of the operation.
Firm jobs are only affected by this parameter if the planning parameter Preserve Pre-Released Production Dates is selected. If Preserve Pre-Released Production Dates is cleared, the materials are planned at the start of the operation.