Figure 12 describes the ON–Bar backup sequence. The onbar-driver builds and sends a list of storage spaces to the Backup Scheduler. The Backup Scheduler creates a backup session. It might start one or more onbar-worker processes. It then assigns backup tasks to the onbar-worker processes.
Once all the storage spaces are backed up, the onbar-driver sends a list of logstreams (logical-log data) to the Backup Scheduler that assigns the tasks to onbar-worker processes. Each onbar-worker process is associated with a coserver and a storage-manager instance. Once an onbar-worker process starts, it might be active after the backup or restore session is completed. An onbar-worker can process parts of several backup or restore sessions in its lifetime.
Each onbar-worker transfers data between the database server and the storage manager until the backup request is fulfilled. When an onbar-worker completes its task, it waits for the next task from the Backup Scheduler. If no new task is assigned in a user-specified amount of time, the onbar-worker shuts down. You can set the number of minutes that the onbar-worker processes wait in BAR_IDLE_TIMEOUT in the ONCONFIG file.
If the Backup Scheduler has new tasks to assign and not enough onbar-worker processes are running to complete the task, it calls the start_worker script to start one or more new onbar-worker processes.
It is recommended that you start onbar-worker processes automatically, but if you want to start them manually, see Using start_worker.sh to Start onbar_worker Processes Manually (XPS). If you have set BAR_WORKER_MAX = 0, you must start a new onbar-worker manually.
After each object is backed up, ON–Bar updates the emergency backup boot file on the coserver that is local to the onbar-worker and the sysutils database. The emergency backup boot file is on the coserver of the onbar-worker that backed it up.
To monitor the status of backups, restores, and onbar-worker activities, use the onstat -g bus or onstat -g bus_sm options or check the Backup Scheduler tables in the sysmaster database. For more information, see Monitoring the Backup Scheduler Status and Backup Scheduler SMI Tables.