Database Reference
In-Depth Information
Configuring Retention Policies
Retention policies are configured in RMAN using the
CONFIGURE
command. When config-
uring a redundancy configuration policy, you will use the
CONFIGURE
command with the
RETENTION POLICY TO REDUNDANCY
keywords, as shown here:
RMAN> configure retention policy to redundancy 1 ;
To configure a recovery-window retention policy, you use the
CONFIGURE
command with
the
RETENTION POLICY TO RECOVERY WINDOW OF DAYS
keywords, as shown here:
RMAN> configure retention policy to recovery window of 2 days;
To disable the retention policy, use the
CONFIGURE
command with the
RETENTION POLICY
TO NONE
keywords, as shown here:
RMAN> configure retention policy to none;
Compression
RMAN has long offered
white-space compression
. Essentially, this means that blocks
in a data file that are not used do not get backed up. White-space compression is quite
helpful for a database that is sized quite large but contains little data. It is less helpful
for well-packed databases.
In these cases, you will want to take advantage of actual
backup set compression
.
This is compression not unlike that available with operating system programs like
pkzip
,
gzip
, and
compress
. Oracle Database 12
c
offers two flavors of compression,
zlib
and
bzip2
(the default).
Zlib
is designed to compress with a minimum of CPU impact.
The result is often a slightly bigger backup image than you get with the
bzip2
compres-
sion format.
You can configure compression as a default value with the
CONFIGURE COMPRESSION
ALGORITHM
command followed by the compression format name, as shown in this
example:
RMAN> configure compression algorithm 'high';
To actually perform a backup with compression, you will need to configure the default
device type to use compression, or you will have to use the
AS COMPRESSED
keyword when
issuing the
BACKUP
command. Here is an example of configuring the default device type to
use compression:
RMAN> configure device type disk backup type to compressed Backup Set;
And here is an example of using the
AS COMPRESSED
keyword when creating a backup:
backup as compressed Backup Set database plus archivelog;
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