Use

 The order change and order execution functions in SAP R/3 only support forward interchangeability (A B; in forward interchangeability, a component B can substitute component A, but the reverse is not possible.) Therefore, SAP R/3 always interprets the original item in an in-house production order as an item of the predecessor, while it always interprets the substitute item as an item of the successor.In SAP APO, however, two components A and B can also be fully interchangeable (A B).In the case of full interchangeability, therefore, the original item in an in-house production order could contain the predecessor component A or the successor component B.If the original item contains the successor component B, it is possible that the automatic adjustment of the dependent requirements might not always lead to the desired result after a manual change to the receipt quantity in SAP R/3. If you increase the receipt quantity for a manufacturing order, SAP R/3 sets the quantity of the original item B to the new total quantity.SAP R/3 sets the quantity of the substitute item A to zero.However, the product being discontinued A should actually be used up first.The same applies to the backflush.