ATP for Order Create vs Order Release

Question

In SAP there is an option for different ATP checks when creating a production order and when releasing a production order.  I'm not sure I understand the behavior we are seeing in our system.  Could be I have a fundamental misunderstanding of the functionality.
In our configuration, ATP for production order create takes into consideration open purchase orders.  ATP for order release does not.  When I go into CO06/CO09 using the checking rule for order create, I see the commitments which include the open purchase order quantities.  When I go in using the checking rule for order release, my expectation is that the commitments for the purchase order quantities will not be there.  Nonetheless, those commitments appear.  I'm receiving missing parts when I'm trying to release a production order even though there is sufficient material not committed to released production orders.
I hope that makes sense.  Any guidance would be appreciated.

Answer 1

Yes.  We have a different checking rule in OPJK for production order create (YO) and one for production order release (YP).  YO includes purchase orders as a supply element in the check and YP does not.  Other than that, they are identical.
I am saying that when looking at CO09 with YP, I saw commitments based on purchase orders.
Purchase orders are a supply element.
MD04 - 18,606 on hand.  Order reservations for 1,512, 9,329, and 709 are for released orders.  The order reservations for 18,657 and 23,322 are for created orders.
CO09 - Checking Rule YO.  Because of purchase order for 45,000, all quantities are confirmed.
CO09 - Checking rule YP.  All quantities still confirmed.