purchase requesation are automatically converting to planned order in next mrp run

Hi Sap Guru,

   I have a query regarding MRP Run

i am using planning strategy 60 &

individual/collective indicator for child material blank

procurement type external   F

System is generating planned order.

if i am changing

individual/collective indicator for child material 2

procurement type external   F

System is generating Purchase Requestation.

we are using background mrp run for every 4 hour

in that both MTS & MTO material requirment are clubbed of in a single planned order

so my doubt is after maintaining

procurement type external   F why system is generating planned order instead of pr.

Any body please put some light on it.

i have searched lot of thread i have not got any satisfactory answer.

Thanks & Regards

Sandeep Kumar Praharaj