BAR_MAX_BACKUP configuration parameter

Use the BAR_MAX_BACKUP parameter to specify the maximum number of parallel processes that are allowed for each command.

onconfig.std value
0
if value not present
4
units
processes
values
0 = Maximum number of processes allowed on system
1 = Serial backup or restore
n = Specified number of processes created
takes effect
When starts
When you reset the value dynamically in your onconfig file by running the onmode -wf or equivalent SQL administration API command.

Although the database server default value for BAR_MAX_BACKUP is 4, the onconfig.std value is 0.

Both UNIX™ and Windows™ support parallel backups.

Specify serial backups and restores

To perform a serial backup or restore, including a serial whole system backup or restore, set BAR_MAX_BACKUP to 1.

Specify parallel backups and restores

To specify parallel backups and restores, including parallel whole system backups and restores, set BAR_MAX_BACKUP to a value higher than 1. For example, if you set BAR_MAX_BACKUP to 5 and execute an command, the maximum number of processes that creates concurrently is 5. Configure BAR_MAX_BACKUP to any number up to the maximum number of storage devices or the maximum number of streams available for physical backups and restores. groups the dbspaces by size for efficient use of parallel resources.

If you set BAR_MAX_BACKUP to 0, the system creates as many processes as needed. The number of processes is limited only by the number of storage spaces or the amount of memory available to the database server, whichever is less.

The amount of memory available is based on SHMTOTAL. performs the following calculation where N is the maximum number of processes that are allowed: 
N = SHMTOTAL / (# transport buffers * size of transport buffers / 1024)

If SHMTOTAL is 0, BAR_MAX_BACKUP is reset to 1. If N is greater than BAR_MAX_BACKUP, uses the BAR_MAX_BACKUP value. Otherwise, starts N backup or restore processes.