BAR_MAX_BACKUP (IDS)

onconfig.std value

0

if value not present

4

units

onbar processes

range of values

0 = maximum number of processes allowed on system

1 = serial backup or restore

n = specified number of processes spawned

takes effect

When onbar starts

The BAR_MAX_BACKUP parameter specifies the maximum number of parallel processes that are allowed for each onbar command. Both UNIX and Windows support parallel backups. Although the database server default value for BAR_MAX_BACKUP is 4, the onconfig.std value is 0.

Specifying Serial Backups and Restores

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

ON–Bar ignores the BAR_MAX_BACKUP parameter for a whole-system backup because they are always done serially.

Specifying Parallel Backups and Restores

To specify parallel backups and restores, set BAR_MAX_BACKUP to a value other than 1. For example, if you set BAR_MAX_BACKUP to 5 and execute an ON–Bar command, the maximum number of processes that ON–Bar will spawn 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.

If you set BAR_MAX_BACKUP to 0, the system creates as many ON–Bar processes as needed. The number of ON–Bar 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_BACKUP is reset to 1. If N is greater than BAR_MAX_BACKUP, ON–Bar uses the BAR_MAX_BACKUP value. Otherwise, ON–Bar starts N backup or restore processes.