I had a user that called me about jobs not running on a 9i database. I logged in and found a complete mess. Broken jobs, some DBMS_JOB calls would hang, jobs existed for users that no longer existed (I didn't even know that was possible!).
Because things were such a mess I just wanted to remove all the jobs and start from scratch. But I needed to drop jobs for a user that no longer existed. Using DBMS_JOB even SYS does not have complete control of jobs. How can I remove a job for a user that no longer exists?