BAR_MAX_RESTORE configuration parameter

Use the BAR_MAX_RESTORE parameter to specify the maximum number of parallel restore processes that are allowed during an ON-Bar restore operation.

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

Both UNIX™ and Windows™ support parallel restores.

Specify serial restores

To perform a serial restore, including a serial whole system restore, set BAR_MAX_RESTORE to 1.

Specify parallel restores

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

If you set BAR_MAX_RESTORE to 0, the system creates as many ON-Bar restore processes as needed. The number of restore 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. ON-Bar performs the following calculation where N is the maximum number of ON-Bar processes that are allowed:

N = SHMTOTAL / (# transport buffers * size of transport buffers / 1024)

If SHMTOTAL is 0, BAR_MAX_RESTORE is reset to 1. If N is greater than BAR_MAX_RESTORE, ON-Bar uses the BAR_MAX_RESTORE value. Otherwise, ON-Bar starts N restore processes.