Parallel Backup of the Same Data files in Oracle 11g RMAN
In Oracle Database 11g RMAN, the channels can break the datafiles into chunks known as “sections.”
we can specify the size of each section. Here’s an example:
RMAN> run {
2> allocate channel c1 type disk format ‘/backup1/%U’;
3> allocate channel c2 type disk format ‘/backup2/%U’;
4> backup
5> section size 500m
6> datafile 6;
7> }
2> allocate channel c1 type disk format ‘/backup1/%U’;
3> allocate channel c2 type disk format ‘/backup2/%U’;
4> backup
5> section size 500m
6> datafile 6;
7> }
This RMAN command allocates two channels and backs up the users’ tablespace in parallel on two channels.
Each channel takes a 500MB section of the datafile and backs it up in parallel. This makes backup of large files faster.
When backed up this way, the backups show up as sections as well.
RMAN> list backup of datafile 6;
…
…
…
List of Backup Pieces for backup set 901 Copy #1
BP Key Pc# Status Piece Name
——- — ———– ———-
2007 1 AVAILABLE /backup1/9dhk7os1_1_1
2008 2 AVAILABLE /backup2/9dhk7os1_1_1
2009 3 AVAILABLE /backup1/9dhk7os1_1_3
2009 3 AVAILABLE /backup2/9dhk7os1_1_4
Some points to remember about multisection backups include:
•If the section size is larger than the file size, RMAN does not use a multisection backup for the file.
•If the section size is so small that more than 256 sections would be produced, RMAN increases the section size such that 256 sections will be created.
•SECTION SIZE and MAXPIECESIZE cannot be used together.
•A backup set never contains a partial datafile, regardless of whether or not it is a multisection backup.
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