Hi Eric,
In case of MTO Scenario with strategy as 20 for FERT material, when you run MRP using MD50 againts the sales order planned orders will be generated for FERT and its dependent materials of BOM. All these planned orders will have account assignment category as sales order ie; the link between sales order and planned order. In case of Raw materials also if you want to stock them specific to sales order then in material master MRP 4 view maintain ind/coll indicator as 1.
In case if you are using strategy 50 planning without final assembly when you run mrp planned orders will be generted for FERT and all dependent BOM materials againt the FERT demand maintained in MD61. But this planned orders will be non convertable planned orders. If you maintain ind/coll indicator as 1, upon receving of sales order if you run MRP MD50 againts the sales order planned orders convertable will be generated for all the dependent materials will account assignment category as sales order.
In both the cases in table PLAF if you input the sales order number you can get all the planned orders. You can also see the details in report MD4C by inputing the sales order. Entire tree structure will be displayed.
Refer the below doc which i posted on Stg 50.
http://scn.sap.com/docs/DOC-51783
Thanks & Regards,
Ramagiri