Databases Reference
In-Depth Information
If there are no backups older than 30 days, RMAN will present the following:
RMAN> delete backup of database completed before 'sysdate-30';
using channel ORA_DISK_1
specification does not match any backup in the repository
RMAN>
How It Works
The
allocate channel for maintenance
command is meant to be used for maintenance tasks such as a
change
,
delete
, or
crosscheck
operation. You can use maintenance channels only at the RMAN prompt. That is, you can't
use maintenance channels within a
run
block. You can also allocate a maintenance channel automatically. Whether
you allocate a maintenance channel manually or automatically, you can't use it for a backup or restore operation. You
won't have to allocate a maintenance channel when executing a
maintenance
command, such as
crosscheck
,
change
,
or
delete
, against a disk-based file (such as an archived redo log, for example), because RMAN preconfigures an
automatic disk channel for those operations.
■
As long as you configure at least one channel for each device type you're using, you don't need to use
maintenance channels. RMAN recommends preconfiguring the channels of tape and disk instead of using the maintenance
channel command. Since RMAN always comes configured with a disk channel, this means you must configure the tape
channel as well to avoid using the
allocate channe
l command in each
run
block in preference to configuring persistent
settings for the channels.
Note
Suppose your current backup strategy uses only disk, but you have several old tape backups you want to get rid of.
You can allocate a maintenance channel for performing the deletion of the tape backups by using the dummy sbt API
(because the media manager isn't available any longer). You can then use the
delete obsolete
command to remove
the tape backups. Here's an example showing how to do those things:
RMAN> allocate channel for maintenance device type sbt
parms 'SBT_LIBRARY=oracle.disksbt,
ENV=(BACKUP_DIR=/tmp)';
RMAN> delete obsolete;
Although the media manager isn't available any longer, RMAN simulates a callout to the media management layer
(MML) and successfully initiates the
maintenance
command to delete the old tape backups you want to get rid of.
Creating a Backup Retention Policy
Problem
You're in charge of coming up with a backup retention policy for your enterprise. You want to create a retention policy
to optimize storage space and other expenses involved in retaining backups.
