M R P - I PP

Q: We have an assembly 'A' using a subassembly 'B'. 'B' in turn uses raw material 'C'. Item 'A' is an MPS and is duly marked in Material Master. Item 'B' and 'C' are marked as 'PD'. When demand for 'A' is entered and MPS is run , upto which level the requirements are taken care of?
A: MRP can be run depending on your requirement. For example:

1. Single Item / Single Level from MPS - Transaction Code MD42 - Only the top MPS item ( 'A' in this case) is planned and dependent requirements will be passed to MRP item ( 'B' ) . Run MRP, Transaction MD02 on 'B' to plan it and all MRP items below .
2. Single Item / Multi Level from MPS - Transaction Code MD41 - All levels are planned - A , B & C
3. Total Planning from MPS online or background - Transaction Code MD40 or MDBS

Without marking the checkbox " Process MRP materials" is like case ( 1) above and with the checkbox marked is like case (2 ).