Recovering Data Using an External Backup and Restore

An external backup and restore eliminates the downtime of systems because the backup and restore operations are performed external to the Informix system. ON–Bar does not move the data during the backup or physical restore. An external backup allows you to copy disks that contain storage-space chunks without using ON–Bar. When disks fail, replace them and use third-party software to restore the data, then use ON–Bar for the logical restore. For more information, see What Is Restored in an External Restore?.

The following are typical scenarios for external backup and restore:

• Availability with disk mirroring. If you use hardware disk mirroring, you can get your system online faster with external backup and restore than with conventional ON–Bar commands.
• Cloning. You can use external backup and restore to clone an existing production system for testing or migration without disturbing the production system.

Figure 20 shows how to perform a backup using mirroring.

Figure 20. Performing a Backup with Mirroring

In this configuration, the database server is running continuously, except for the short time when the database server is blocked to break the mirror. The mirrored disks contain a copy of the database server storage spaces. To create a backup, block the database server to stop transactions and disable mirroring. The mirrored disks now contain a copy of the consistent data at a specific point in time. After disabling mirroring, unblock the database server to allow transactions to resume and then backup the logical logs. Copy the data from the offline mirrored disks to backup media using external commands. Now you can resume mirroring.