The correct answer is - TC OVZJ has a setting for Availability Check Rule REVFP as "E" (Dialog box in the case of shortages (batch/BAPI dlv. prpsl) as opposed to Blank (Dialog box in the case of shortages (batch/BAPI full dlv.) , This causes the rescheduling job to work without freeing up part allocated stock and change requirements alongwith changing supplies.
I got it from SAP. Thanks everyone for their contribution and help.
