Oracle RMAN Multi-Section Feature

RMAN can optionally break up large files into sections and back up and restore these sections independently. This feature is built into RMAN. You can use it by creating multisection backups, which break up the files generated for the backup set into separate files. This can be done for backup sets and image copies.

Each file section is a contiguous range of blocks of a file. Each file section can be processed
independently, either serially or in parallel. Backing up a file into separate sections can improve the
performance of the backup operation, and it also allows large file backups to be restarted.

Multisection image copies reduce the image copy creation time for large data files, in particular
benefiting Exadata environments.

Each section can be processed independently, either serially or in parallel. Backing up a file into
separate sections can improve the performance of the backup operation, and it also allows large file
backups to be restarted.

You should not apply large values of parallelism to back up a large file that resides on a small
number of disks, because that would defeat the purpose of the parallel operation. Multiple
simultaneous accesses to the same disk device would be competing with each other.

Let us have a quick demo:

Case 1:

• Multi-section , one channel [parallel=1], using backupsets.
  Two backup pieces are produced based on the section size , one channel.

Increase Parallelism:

Case 2:

• Multi-section , one channel [parallel=2], using backupsets.
  Two backup pieces produced based on the section size, 2 channels.

Case 3:

Backup as copy:
— (Note that in this case and although of using 2 channels [parallel=2], but the final output is one backup piece , as this is an image copy)

Thanks
Ahmed