> I've looked but so far found nothing giving me
> the option to overwrite instead of append
> the dsmsched.log file on the client at the start
> of scheduled backups/archives.

From my dsm.sys file:

        schedlogretention       2 s

This causes my schedule log to be pruned of all entries older than two
days.  The "s" causes pruned entries to be saved to a dsmsched.pru
file which gets backed up and is then deleted due to this line, also
from dsm.sys:

        postschedulecmd         "rm -f /tmp/sa/dsmsched.pru"

Try tinkering with this concept to handle your situation, perhaps a
one day retention would be appropriate in your case.
schedlogretention is documented on page 138 of the ADSM manual "Using
the Unix Backup-Archive Client".  postschedulecmd is documented on
page 130 of the same manual.

Regards,
Chuck