Hi Mustafa,
The MRP type maintained for the material decide where the material will be planned actually.
A - Finished product planned in R/3
B - Product planned in APO and in available in the BOM of A.
Now if B is planned in APO, then when the planning is done for A, B will not be considered in the MRP run. In that case reservation will not be generated.
Can you please explain your requirement in detail.
Br,
BVN