You need to take a good look at the scheduler session log, for
starters (and also check the dsmerror.log and dsmwebcl.log).  A
common cause for missed schedules is that the previously started task
is still running, as for example where a client backup gets longer
and longer each day due to growth.  See other common causes in entry
"Schedule, missed" in http://people.bu.edu/rbs/ADSM.QuickFacts, which
also points to IBM references on the topic.

You don't cite your client software level.  If it is base level
(e.g., 5.3.0.0) or early, by all means apply current maintenance.

    Richard Sims