R12 upgrade performance issue

During the test R12 upgrade following script is taking over 7 hours to complete.  What I have found is that all workers are running this script simultaneously and all of them are contenting each other for library cache lock.  I checked a few of the sessions and found they are all runing same sql .  So I am planing to run a single thread instead of  leting all workers to execute it.

aptppupg.sql

Following parameters are from the scripts.    If I just hardcode value for  l_num_workers to 1 will run on single worker instead of all?

l_worker_id       number  := &&3;