APO CTP is not updating when sales order quantity is reduced

Hi Team,

CTP is not updating the planned orders or PPDS PReq corectly when quantity changes in sales order.

When we create sales order in ECC, it creates PPDS Planned orders and PPDS preqs.But
while reducing SO quantity it is not reducing the Planned orders and Preqs.

The reduction is not happening because the purchase requisition already created in PP firm , hence
CTP heuristics could not reduce the quantity of the same.

Kindly

Regards,

Rakesh