Master Planning is showing to purchase when there is inventory on-hand

Hi

Master scheduling was run for all the items. In planned orders, it created lines for item XXX as 'planned purchase order'. There is on-hand inventory for the item. Then i went to the released product of that item->plan action tab->Net requirements->Update->Master scheduling. On doing this, it updated the lines in Net requirement form and gave on-hand line and suggested a transfer journal. 

Do i need to do this all the time, assuming that there are 200,000 items? how do i make the master plan to give the desired result. 

Thanks

Harsha