Parallel Backup

Use

You can use BRBACKUP and BRARCHIVE to back up your Oracle database to several backup devices in parallel. The backup devices can be tape or disk drives. Parallel backup reduces the backup time and allows unattended operation (that is, backup in unattended mode).

Parallel backup is especially useful for large databases. For more information, see Parallel Backup of Large Databases to Disk with BRBACKUP.

Features

• Parallel backup is possible to local or remote backup devices.

• If the backup devices used support hardware compression, use this by setting the
init.sap parameter compress = hardware. You can also make parallel backups with software compression, using compress = yes. For more information, see compress.
• When you perform parallel backups to several backup devices, BRBACKUP attempts to optimize the distribution of the database files among the backup volumes using load balancing, as follows:

• BRBACKUP attempts to balance the load equally among all the backup devices, which is called time optimization. If this is not possible, it attempts to divide the dataset equally among the individual backup devices, which is called size optimization.
• Whenever possible, BRBACKUP saves files from one disk on one volume in one backup device, in order to minimize drive head movement during the backup.

• BRARCHIVE only uses the parallel backup option to tape when you start archiving with
brarchive -ss or brarchive -ssd. In this case, the offline redo log files for archiving are saved to both volumes in parallel (or saved and then deleted). For more information, see -s|-sc|-ds|-dc|-sd|-scd|-ss|-ssd|-cs|-cds.

• The addresses of the tape devices are defined in the following
init.sap parameters:

• 
  
tape_address
• 
  
tape_address_rew
• 
  
tape_address_arch
• 
  
tape_address_rew_arch

• If the
-ss or -ssd option is used, BRARCHIVE only uses the first two tape devices in the list. The addresses of the directories on disk are defined in the init.sap parameter backup_root_dir or stage_root_dir.

This is an example of the entries required in the init.sap initialization profile for parallel backup:

• Device type:
  
backup_dev_type = tape|disk|pipe|stage
• Addresses for tape devices:
  
tape_address = (/dev/rmt/0hnc, /dev/rmt/1hnc)
tape_address_rew = (/dev/rmt/0hc, /dev/rmt/1hc)
• Addresses for directories on hard disk:
  
backup_root_dir = (/backup/dir1, /backup/dir2)
• Compression parameters:
  
compress = no|software|hardware
• Tape size:
  
tape_size = 18G|16G

• The number of parallel copy processes normally corresponds to the number of backup devices available. You can change this setting with the
init.sap parameter exec_parallel or the command option -e|-execute.