Hi,
First change the task status from 4 to 5 for existing transaction(old transaction) on database which needs to be cancelled/reversed using program /POSDW/CHANGE_TASKSTATUS and then pass your old transaction to /POSDW/PIPEDISPATCHER.
Task status will turn to 8-Cancelled.
Thats it.
Later whenever you will run /POSDW/PIPEDISPATCHER for new transaction it should get processed.
I've never done this. But I think this will work.
All the best !!
Thanks,
Vikrant Mohite.