Hi!

Today I realized that some of our scheduled backups were silently
ignored. Here are some details:

In the DP schedule files, you can specify "-at HH:MM" for the time when to
execute the specification. First surprise is that Data Protector reports a
"syntax error" if you specify "MM" that is different from "00", "15", "30",
"45". That is you can only specify multiples of 15 minutes.

In our complex scenario with many hosts and devices, I wrote a backup planner
that reads high-level specifications and the schedules DP backups
(i.e. creates the schedule files, logs, statistics, iCalendar, estimate of
media usage, data protection validation, etc.), considering which
specification uses which resorces, the number of available licenses, holidays,
weekends, etc.

Now that some incremental backups just take 4 minutes or so, the created
schedules would be quite tight. For example:
17:00 A
17:00 B
17:10 A
17:10 B
17:30 C
17:30 D
17:40 B
17:40 D

A to D are backup specifications and the first occurrences are incremental
backups, followed by levelled backups.

As DP cannot schedule at 17:10, the backup was scheduled at 17:00 also. The
expectation was that it would be queued until the first one is finished.
However, as it seems, DP just silently ignored the second occurrence of A, B,
C, and D.

Can anybody explain this arbitrary restriction to muliples of 15 minutes?
Cron can do a better job for 20 years now.

The solution seems to be to specify a minimum duration of 15 minutes per
backup session, even though the backup just needs a few minutes. This will
fragment the time space a lot, being unable to fill the gaps. Also this will
minimize device usage as there are unnecessary breaks between backups. My
scheduler could handle free time slots down to one second, but it does not
make any sense with DP.

BTW: How do you guys keep track when which backups are scheduled to avoid
queueing conflicts caused by scheduling and device usage?

Regards,
Ulrich