If you need
to preserve an online backup for a specified amount of time, RMAN normally
assumes you might want to perform point-in-time recovery for any time since
that backup to the present. To satisfy this scenario, RMAN keeps the archived
logs for that time period (unless you specified NOLOGS). However, you may have
a requirement to simply keep the specific backup (and what is necessary to keep
it consistent and recoverable) for a specified amount of time—for example, for
two years. You do not have the intention of recovering to a point in time since
that backup, but you just want to be able to recover to the exact time of the
backup, and no later. You also want to maintain a retention policy that keeps
your backup area free of clutter, so making it reach back two years is not
acceptable. This is a common need, when meeting business or legal requirements
for data retention.
An archival
backup solves this problem. If you mark a backup as an archival backup, that
attribute overrides any configured retention policy for the purpose of this
backup. You can retain archival backups such that they are either considered
obsolete only after a specific time that you specify, or never considered
obsolete. If you want to specify the latter, you need to use a recovery
catalog.
An archival
backup also guarantees that all of the files needed to restore the backup are
included. RMAN includes the data files, archived log files (only those needed
to recover an online backup), and the relevant autobackup files. All these
files must go to the same media family (or group of tapes).
You can
also specify a restore point to be created, which has the same SCN as the
archival backup. That essentially gives a meaningful name to the point of time
the backup was made.
After an
archival backup is created, it is retained for as long as specified. Even if
you have a much smaller retention window and run the DELETE OBSOLETE command,
the archival backup remains.
This backup
is a snapshot of the database at a point in time, and can be used to restore
the database to another host for testing purposes, for example.
Note: Archival backups cannot be written
to the Flash Recovery Area. So if you have one, you must provide a FORMAT
clause to specify a different location.
Creating
Archival Backups with EM
To create
an archival backup using Enterprise Manager, perform the following steps:
·
Select
Availability > Schedule Backup > Schedule Customized Backup.
·
Follow
the steps of the Schedule Customized Backup wizard until you are on the
Settings page.
o
Click
Override Current Settings and then the Policy tab. In the Override Retention
Policy section, you can select to keep a backup for a specified number of days.
A restore point is generated based on the backup job name. You probably also
want to specify a different destination for the backup files; to do this, use
the Device tab.
Creating
Archival Backups with RMAN
Use the
following syntax to create an archival backup using RMAN:
BACKUP ... KEEP
{FOREVER|UNTIL TIME 'SYSDATE + <n>'} RESTORE POINT <restore_point_name>
The UNTIL TIME
clause enables you to specify when the archival backup is no longer immune to
the retention policy. You can optionally specify FOREVER, meaning that the
backup is an archival backup until you take some other action to change that.
Optionally,
use the RESTORE POINT clause to specify the name of a restore point to be
associated with this backup.
