I have come across occasions when a Developer or a DBA has "killed" a job only because "it was hung". If your user or Developer points you to a job that "seems to be 'hung'", as a DBA, it is your responsibility to determine the status of the job from the database instance perspective, not from the user's perspective. Besides the GUI Enterprise Manager screens, Oracle provides numerous views that you can use to monitor the job. Learn to make use of V$SESSION, V$SESS_IO, V$SESSTAT, V$SESSION_WAIT, V$SESSION_EVENT, V$ACTIVE_SESSION_HISTORY to monitor a session.
Never kill and restart a job without at least determining (or to a reasonable degree of confidence) what caused the job to appear to be 'hung' and what action you need to take to ensure that the behaviour doesn't repeat the next time the job is re-run.
If you merely kill a job and expect it to perform better when it is restarted, without determining and fixing the causes, you are likely to incur the displeasure of the user.
As a professional, one of the attributes expected of you is "being able to diagnose a cause for a symptom".