STR pegging with Sales Order

Hello Experts,

I have a scenario in which STR (Stock transport requisition) is FIXED pegged with Forecast and Sales Order.The requirement is, I want to fulfill sales order only with this STR not the forecast.

I am able to change the STR quantity with the pegged quantity with sales order using BAPI ( ie: STR Qty = Pegged Qty of SO) But when I see the pegging overview, in product view (/SAPAPO/RRP3),System is fulfilling forecast first and then sales order.

I tried to change the STR quantity manually in product view,but still it is pegged with forecast first which I dont want.

I want STR to be pegged only with Sales order not with any other order.

Do this require any setting somewhere in SPRO? or this is a normal case in SAP APO? or Do I need to break pegging relationship first then create new pegging relationship with SO only?

Please advice.

Regards,

Saurabh