PPDS Heuristic

Hello experts, Last week, incorrect forecast which is 10 times the normal levels was released from DP, the PPDS planning run (SAP_PP_002 heuristic) created high planned orders accordingly. Forecast was corrected and re-released, but there are still high volume planned order remaining in the system. This is causing the MRP for Raw materials to generate high purchase reqs in ECC. I was hoping PPDS heuristic will delete all planned orders that are not fixed and outside of the Planning time fence and re-plan based on the corrected forecast. Or does there need to be a seperate deletion job before every PPDS planning run. I am trying to understand how PPDS heuristic SAP_PP_002 heuristic works. Thanks Tej