To enable VOB database snapshots, run
vob_snapshot_setup.
This command causes the
Rational® ClearCase® scheduler
to run
vob_snapshot periodically (daily, by default) on
the VOB database. The
vob_snapshot_setup and
vob_snapshot reference
pages explain these operations. Whenever you enable a VOB for snapshot backups,
you must take additional steps to ensure that the backup is complete and can
be recovered with little or no data loss:
- Back up the entire VOB storage directory, including any remote storage
pools (see If the VOB has remote storage pools),
as soon as possible after each vob_snapshot completes.
You do not have to lock the VOB during this backup. If you complete this backup
within 30 minutes of the time vob_snapshot completes, you
are less likely to lose data when the VOB is restored. You can reduce backup
time by excluding the VOB database (db directory) itself
from the backup. (It has already been backed up by vob_snapshot.)
- Back up the snapshot itself. This is especially important if the snapshot
is copied to a location on the same physical device as the VOB. If that device
fails and the snapshot has not been backed up to other media or copied to
a different device, the backup is useless.
Note: Deferred deletion of source containers is enabled by the vob_snapshot_setup program
and is intended to optimize chances that a pool backup that follows a vob_snapshot within
30 minutes will include all source containers to which the database snapshot
holds a reference. When a container is replaced by new version data (for example,
during checkin), the new container is created and the old one is deleted.
If deferred deletion is enabled, the old container is added to a list of pending
deletions and removed after 30 minutes.
Deferred deletion increases
disk space requirements in a active VOB. On platforms running Linux or the UNIX system,
you can run the kill –HUP command
on the vob_server process to send deferred deletion statistics
to its log file. When checkvob examines source pools, it
reports any containers on the deferred deletion list. The deferred deletion
list is written every five minutes to the file delete_list.db in
the VOB storage directory.