The BAR_WORKER_MAX configuration parameter determines how many storage spaces and logical logs can be backed up or restored in parallel on each storage manager. It also specifies the maximum number of onbar-worker processes that the database server automatically starts for this storage-manager instance. If the BAR_WORKER_MAX value is 0, you must start the onbar-worker processes manually.
For example, to start five onbar-worker processes in parallel, set BAR_WORKER_MAX to 5. Set BAR_WORKER_MAX to the number of storage devices available to the storage manager. If the database server has multiple storage managers configured, the number of parallel operations is the sum of BAR_WORKER_MAX values for all storage managers. The maximum number of onbar-worker processes that run simultaneously depends on the capabilities of the storage manager.
If onbar-worker processes for a specific storage manager have special start-up requirements, such as environment variables, you can specify these by editing the start_worker script file. For information, see Using start_worker.sh to Start onbar_worker Processes Manually (XPS). If storage managers have dynamic requirements for onbar-worker processes, you might have to start them manually.
You can specify serial backups and restores with Extended Parallel Server in two ways:
You must start the onbar-worker processes manually before you can back up or restore data.
The database server starts one onbar-worker process and backs up or restores the data serially for this storage-manager instance.