Oracle : Ошибка ORA-15130

"diskgroup \"%s\" is being dismounted"
*Cause: The diskgroup is being dismounted by request or because an I/O
error was encountered that could not be handled by taking the
disks offline. A disk cannot be offlined whenever doing so
could result in all copies of a redundant extent being unavailable.
*Action: Repair the hardware problem and re-mount the diskgroup.
Refer to the alert log to determine which disks have failed.

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