>I want to alter a database job so that it executes on the 3rd Saturday of each month
This is not all that easy to do with DBMS_JOB.
I had to implement this requirement,
I have the job start EVERY Saturday.
Within the code I have it check and if not the 3rd Saturday,
then exit & do nothing. Only on the 3rd Saturday would
the process continue to run & do what is needed.