Changing Reservations

Dear Experts,

When one of my users creates a PM Order and enter components with the availability check system gives the message that the stock is not sufficient. But since this is a priority order stock has to be released from some other order and allocated to this. So I searched and found some orders where I can release stocks. But the problem is how can I release stocks. One option is to delete the material line of the order and re-enter once the reservation for the priority order has been made. But this is not a good method as it could lead to mistakes. So is there a better method like deactivating lines where reservation is removed.

Additionally,is there a way to reserve a particular serial item to a PM Order?

Cheers

Deepal