Disk mirroring is automatically deactivated when one of the two physical devices fails. When a read or write to a mirrored device is unsuccessful, Adaptive Server prints error messages. Adaptive Server continues to run, unmirrored. You must remirror the disk to restart mirroring.
Use the disk unmirror command to stop the mirroring process during hardware maintenance:
disk unmirror name = "device_name" [, side = { "primary" | secondary }] [, mode = { retain | remove }]
The side option to the disk unmirror command allows you to specify which side of the mirror to disable. primary (in quotes) is the device listed in the name column of sysdevices; secondary (no quotes required) is the device listed in the mirrorname column of sysdevices. secondary is the default.
The mode option indicates whether the unmirroring process should be temporary (retain) or permanent (remove). retain is the default.