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Category :
Database
Resources -> Backup and Recovery
DB Version
:
Oracle 8i /
Oracle 9i
OS Details :
Sun Solaris9
If
the hardware architecture is built around the use of NAS disks then we
have an extra option which decreases the overall time taken for
performing online backups. As you might be already aware of, keeping
tablespaces in backup mode can cause excessive logging since oracle
will begin logging entire block images on the first change to the
block if that block belongs to a tablespace that's been placed in
backup mode.
NAS disks gives the ability of "snapview"
or "snapshot". A snapshot or snapview is the ability to table a
snapshot of the datafiles under hot backup mode to an intermediate
location. Taking a snapshot or snapview of the database is a very fast
operation and is something that will prevent the tablespaces to be in
backup mode for an extended period of time.
Please be aware that any form
of hot backups can be done only if the database is in archivelog mode.
The following steps have to be followed to take hot backups using the
snapview or snapshot method available with NAS disks:
(1) Put all the tablespaces
that are part of the database in backup mode.
Example : alter tablespace
system begin backup;
(2) Suspend all IO operation
on the database by running the following command:
alter system suspend;
(3) Take a snapview or
snapshot of the datafiles, controlfiles and redologs. This operation
should take only a couple of minutes.
(4) Resume IO operation on the
database by running this command:
alter system resume;
(5) Put all tablespaces back
in normal mode.
Example : alter tablespace
system end backup;
Please note that the use of
suspend and resume options should be used only when online backups
using snapview or snapshots of NAS disks are being done. It is not
recommended to use this option for normal hot backups.
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