Prod storage location

My requirement is to find the materials which dont have production stor loc maintained in the material master MRP2 view..

I have got a list from MARC table by filtering the prod storage location field.. I have got 19000 materials without the production storage location..

I am sure that these 19000 materials need not necessarily be production related..

Can anybody give me an idea of how to get a list of materials that are production related..

i.e I want to get a list of materials for which production orders will be created and also for which are going to be issued to production orders...

( I have an idea to get the list of all the materials that are having backflush indicator coz in this plant all the materials are backflushed and for header materials >those which have BOM and routings)

anyother idea from u experts????