What Happens During a Backup Operation?

The database server administrator or operator uses ON–Bar to request a backup operation. When the ISM server receives a backup request from ON–Bar, it creates one or more save sets on the storage media as the data is backed up. The ISM server writes the backup data to storage volumes mounted on storage devices that are attached to the ISM server. ISM uses volume pools to sort specific data onto preselected storage volumes in order to help manage your data. For example, by default ISM writes data from dbspaces to a collection of volumes in the ISMData volume pool and the logical-log files to volumes in the ISMLogs volume pool.

During a backup or restore operation, ISM requests that you mount a labeled storage volume from the appropriate volume pool on one of the storage devices attached to the ISM server. You can label and mount a storage volume when you receive the request from the ISM server, or you can prelabel several volumes and mount them as you need them.

To further automate the labeling and mounting process, you can designate that a specific storage device should handle all storage media that is loaded in it exclusively as ISM media. This arrangement means that you can load a blank tape in a storage device, and the ISM server labels and mounts it when it needs a new storage volume for an ON–Bar backup. For more information, see Managing Storage Volumes.

Figure 2 illustrates how data and requests move between ON–Bar, the ISM server, and the database server during a backup operation. Backup requests are processed in the following sequence:

1. The user uses ON–Bar to start a backup operation.
2. ON–Bar determines what data needs to be backed up.
3. ON–Bar connects to the ISM server.
4. ON–Bar retrieves the data from the appropriate storage spaces or logical logs on the Informix database server, builds a list of backup objects, and passes it to the ISM server.
5. The ISM server creates a save set from the data and writes that save set to the proper storage volumes.
6. The ISM server enters a record of the save sets and the storage volumes in the ISM catalog.

   The ISM server uses the ISM catalog to track the save sets and the volumes to which they are backed up.

7. After the backup operation finishes, ON–Bar disconnects from ISM.
8. ON–Bar creates a save set called the ISM server bootstrap, which contains configuration information about the ISM server for disaster recovery purposes.

   The ISM server writes the ISM server bootstrap to a volume from the ISMData volume pool. You can send the ISM server bootstrap information to the printer that you designated during installation.

9. ON–Bar writes information about the backup to the database server message log and ON–Bar activity log. ISM writes information about the backup to the ISM\2.20\logs\messages log.

Use the ism_watch command to track ISM server activity.

Figure 2. Data Movement During an ON-Bar Backup