Hi Ramesh,
When you run the location Heuristic at DC level system create distribution demand on manufacturing plant. Purchase orders, planned orders and production orders are never created when run the heuristic at DC level. This distribution receipt in the supplying form of purchase requisition. At manufacturing plant in SNP, we usually carries out Planning run for generation of planned orders for inhouse production and purchase requisitions for external procurement. The SNP planning outputs are in the form of purchase requisitions and planned orders. After that we convert the planned order to production/process order in PPDS. After Deployment run, Transport Load Builder (TLB) is run to create shipment orders.
Please refer the SAP help link for more details.
SAP Library - Supply Network Planning
Regards,
R.Brahmankar