Disk mirroring is automatically deactivated when one of the two physical devices fails.
When a read or write to a mirrored device is unsuccessful, SAP ASE prints error messages. SAP ASE continues to run, unmirrored. You must remirror the disk to restart mirroring.
disk unmirror name = "device_name" [, side = { "primary" | secondary }] [, mode = { retain | remove }]