Hi Raju,
It is clear that the planning of your parent material is done in a separate system. Now what happen with the execution. I assume the execution is done in SAP for your parent material and the lower levels. Is this right?
If this is correct, then you will need the planned orders for the header materials for the execution and also in order to explode the BOMs and see your dependent requirements in the lower levels of the BOM. If you have another system to plan the parent material what you can do is to keep the planning in the separate system and transfer the production orders or planned orders to SAP in order to explode the requirements.
Please detail all the process, where the plan is done. How you control your production? Where do you decelerate production and consume the inventory of your components, etc..
Kind Regards,
Mariano