Selection Parameters 
Selection Parameters
The selection parameters determine amongst other things:
You thus determine which type of BOM the system should select.
Use this indicator to assign bills of material from external systems (via a user exit). For more information about the customer enhancements for exploding BOMs from external systems or additional processing of internal BOMs, see the IMG of the Project System.
Use this indicator to determine that the system explodes the BOM completely (multi-level). In this case the system also generates requirements for subordinate assemblies in the network.
This is useful for instance, if you want to generate requirements in advance for components that have a long delivery time or take long to produce. To do so, you also set the Preliminary requirements indicator: The system then creates planned independent requirements or preliminary purchase orders that can be consumed by real requirements later.
If you only set the multi-level indicator but not the Preliminary reqmnts indicator, then you run the risk that the system will generate excess requirements. If afterwards you generate requirements for a superior assembly, materials planning will also generate requirements for the subordinate assembly, since bills of material are always exploded. If however there are already sufficiently large planned independent requirements the system consumes them.
For more information, see
Use this indicator to determine that BOM items that do not have reference points are also selected. In the case of items that the system could not assign automatically, the system prompts you to assign manually.