3163591 - MRP deletes purchase requisitions and recreates them with planning mode 1

If the requirement quantity or date or BOM is changed, then you run MRP with planning mode 1, the existing procurement proposals such as purchase requisitions or planned orders are deleted and recreated.

SAP S/4HANA Cloud 

Standard system design.

You have two options to define the planning mode in MRP :

• Planning Mode 1: Adapt Planning Data
  If the system finds an unfirmed procurement proposal that completely matches a requirement, it reuses this procurement proposal. If the system finds an unfirmed procurement proposal that only partially matches a requirement (for example, the quantity is correct but the date does not suit the requirement), the system deletes this unfirmed procurement proposal and creates a new one. The system explodes the BOM again for the recreated procurement proposals.
• Planning Mode 3: Delete and Recreate Planning Data
  The system deletes all unfirmed procurement proposals and creates new procurement proposals to match the requirement situation.

Firm the procurement proposals if you do not want them to be deleted and recreated by MRP unexpectedly. 
Refer to online help regarding how to firm procurement proposals.

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