You can
configure parallel backups by setting the PARALLELISM option of the CONFIGURE
command to greater than 1 or by manually allocating multiple channels. RMAN
parallelizes its operation and writes multiple backup sets in parallel. The
server sessions divide the work of backing up the specified files.
Example
RMAN> RUN {
2>
ALLOCATE CHANNEL c1 DEVICE TYPE sbt;
3>
ALLOCATE CHANNEL c2 DEVICE TYPE sbt;
4>
ALLOCATE CHANNEL c3 DEVICE TYPE sbt;
5>
BACKUP
6> INCREMENTAL
LEVEL = 0
7> (DATAFILE
1,4,5 CHANNEL c1)
8> (DATAFILE
2,3,9 CHANNEL c2)
9> (DATAFILE
6,7,8 CHANNEL c3);
10>
SQL 'ALTER SYSTEM ARCHIVE LOG CURRENT';
11> }
When
backing up data files, you can specify the files to be backed up by either
their path name or their file number. For example, the following two commands
perform the same action:
BACKUP
DEVICE TYPE sbt DATAFILE '/home/oracle/system01.dbf';
BACKUP
DEVICE TYPE sbt DATAFILE 1;
When you
create multiple backup sets and allocate multiple channels, RMAN automatically
parallelizes its operation and writes multiple backup sets in parallel. The
allocated server sessions share the work of backing up the specified data
files, control files, and archived redo logs. You cannot stripe a single backup
set across multiple channels.
Parallelization
of backup sets is achieved by:
•
Configuring
PARALLELISM to greater than 1 or allocating multiple channels
•
Specifying
many files to back up
Example
•
There
are nine files that need to be backed up (data files 1 through 9).
•
Assign
the data files to a backup set so that each set has approximately the same
number of data blocks to back up (for efficiency).
•
Data
files 1, 4, and 5 are assigned to backup set 1.
•
Data
files 2, 3, and 9 are assigned to backup set 2.
•
Data
files 6, 7, and 8 are assigned to backup set 3.
Note: You can also use the FILESPERSET
parameter to limit the number of data files that are included in a backup set.
