Hot Backups Using Nas 8000 Snapshots; Hot Backups Without Nas 8000 Snapshots; Cold Backups Using Nas 8000 Snapshots; Cold Backups Without Nas 8000 Snapshots - HP StorageWorks 8000 - NAS User Manual

amount of time a database is unavailable when performing a "cold backup". If snapshots will be used,
especially in a highly dynamic environment where data is rapidly changing, be sure to reserve space for
the snapshots in the appropriate volume groups. Snapshots are taken at the file volume level. That is, a
snapshot is taken of a single file volume. If the database data files are distributed across multiple file
volumes, multiple snapshots will be needed. Please refer to the NAS 8000 Users Guide for more
information on snapshots. There are two usual methods for backing up an Oracle database, a "hot
backup" or a "cold backup".

hot backups using NAS 8000 snapshots

A hot backup (also known as an inconsistent backup) is performed by issuing an "alter tablespace"
command and placing the tablespaces (all, or whatever the backup plan calls for) into "backup mode". In
this mode, changes to the tablespace are "logged" by the Oracle engine, but not actually written to the
tablespace until it is returned to "active mode". Performing a hot backup leaves the database in an active
state, available for user access. Being an inconsistent backup implies that if a restore operation were
performed using this backup, a database recovery (along with succeeding transaction logs), would be
required. The first step would be to place the tablespace(s) in "backup" mode via the 'alter tablespace'
command. The snapshot is created via the Command View NAS management GUI, and takes only a
moment to actually occur. Once the snapshot has been taken, the tablespace(s) are put back into "normal"
mode and an 'alter system switch logfile' command is executed to ensure that the archive log can be
applied to the database in the event of a recovery. The snapshot(s) are then backed up and can be deleted.
The database remains available while the snapshot(s) are being taken, and while the snapshot(s) are being
backed up. Be sure to backup the redo/archived logs so that the database can be recovered in the event
that a restore from an inconsistent backup is necessary. Currently, sharing the NAS 8000 snapshot to
make it accessible to a backup engine will force an SMB reset that will reset all SMB connections. This can
crash processes using the database. It is not recommended that the NAS 8000 snapshot mechanism be
used until this problem has been rectified.

hot backups without NAS 8000 snapshots

A hot backup can also be performed without utilizing snapshots NAS 8000. This may be necessary if there
is not enough space available in the volume group for the snapshot to be created. In this scenario, the
backup will perform as expected, although there may be additional system performance degradation due
to the amount of time that the tablespaces will be in "backup mode" and Oracle must journal changes to
the tablespaces, rather than applying them. When the backup completes, be sure to execute an ALTER
SYSTEM SWITCH LOGFILE command after the tablespace(s) are taken out of backup mode to make sure
that the alter tablespace command that took the tablespace out of backup mode is written to the archive log
immediately. This ensures that the archive log can be applied to the database in the event of a crash.

cold backups using NAS 8000 snapshots

A cold backup (also known as a consistent backup) is performed when the database is shutdown normally
and the database data files are made available for backing up (copying, writing to tape media, etc).
Because the database is shutdown, it is no longer available for user access. As well, since the database is
shutdown, the SCN numbers in all of the data files will match, and therefore, a restore operation performed
with this backup would not require a database recovery. Once the database has been stopped, a
snapshot is taken of the file volume(s) containing the database data files. This happens very quickly. After
the snapshot is taken, the database can be restarted, and the snapshot backed up to some other media,
such as magnetic tape. Using this scenario, the time the database is unavailable may be reduced from
hours to mere minutes. Once the backup has completed, the snapshot(s) can be deleted.

cold backups without NAS 8000 snapshots

A cold backup can be performed without utilizing the snapshot feature of the NAS 8000 in the event that
there is not enough available space in the volume group(s) to permit a snapshot operation. However, the
database will be unavailable for the length of time that the backup takes to complete. This could be from
several minutes to several hours depending upon the amount of data to be backed-up and the target media
for the backup.

nvram usage and nvram failures

The NAS 8000 storage subsystem (VA 7xxx) uses dual battery backed-up, mirrored NVRAM to increase
write performance to the hard drives. The NVRAM is mirrored across both controllers in the VA enclosure.
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