Another possible cause: very busy CPU.  The default case for sessions is
a higher priority than jobs.  Jobs with the *EXEC have finished the INIT
state and are just beginning the EXEC state --but really haven't done so.
 A job not being aborted after an ABORTJOB is another symptom of this
type of problem.  What happens is that all of the available CPU cycles
are being consumed by (higher priority) sessions with none left for
(lower priority jobs).  Remember a job needs CPU time to abort....
 
Regards,