Databases Reference
In-Depth Information
In the previous example, we specify a degree of parallelism of 4 for the device type disk. Once you configure
the degree of parallelism, configure channels as follows (assuming you want parallelism of degree 4) using the
parallelism
clause to specify the degree of parallelism:
configure device type disk parallelism 4;
configure default device type to disk;
configure channel 1 device type disk format '/u01/%d_backups/%U';
configure channel 2 device type disk format '/u02/%d_backups/%U';
configure channel 3 device type disk format '/u03/%d_backups/%U';
configure channel 4 device type disk format '/u04/%d_backups/%U';
RMAN will henceforward distribute all your backups over the four disks by default. You can undo the
configuration of parallelism for the disk device in the following manner:
RMAN> configure device type disk clear;
old RMAN configuration parameters:
CONFIGURE DEVICE TYPE DISK PARALLELISM 4 BACKUP TYPE TO BACKUPSET;
RMAN configuration parameters are successfully reset to default value
RMAN>
You can also specify the degree of parallelism for tape backups by using the following command:
RMAN> configure device type sbt parallelism 3;
The previous command uses a degree of parallelism of 3 for all subsequent tape backups. Once again you can use
the
clear
option to revert to the default parallelism setting, as shown here:
RMAN> configure device type sbt clear;
This command will set the degree of parallelism to the default value of 1, which means future tape backups will
not be parallelized.
How It Works
You can parallelize an RMAN backup by using either the
configure
command (as explained in Chapter 5) or the
allocate channel
command to manually specify multiple channels for a backup job.
The
parallelism
clause configures the number of automatic channels of a specific type, disk, or tape that RMAN
allocates to a job. The default degree of parallelism is 1, and you can set the degree of parallelism for both disk and
tape drives, as shown in the “Solution” section of this recipe. RMAN determines the degree of parallelism for a job
based on which device type you specify as the device type for the backup.
