V$ASM_DISKGROUP displays one row for every ASM disk group discovered by the ASM instance on the node.

Column Datatype Description
GROUP_NUMBER NUMBER Cluster-wide number assigned to the disk group (primary key)
NAME VARCHAR2(30) Name of the disk group
SECTOR_SIZE NUMBER Physical block size (in bytes)
BLOCK_SIZE NUMBER Oracle ASM metadata block size (in bytes)
ALLOCATION_UNIT_SIZE NUMBER Size of the allocation unit (in bytes)
STATE VARCHAR2(11) State of the disk group relative to the instance:
  • CONNECTED - Disk group is in use by the database instance

  • BROKEN - Database instance lost connectivity to the Oracle ASM instance that mounted the disk group

  • UNKNOWN - Oracle ASM instance has never attempted to mount the disk group

  • DISMOUNTED - Disk group was cleanly dismounted by the Oracle ASM instance following a successful mount

  • MOUNTED - Instance is successfully serving the disk group to its database clients

  • QUIESCING - CRSCTL utility attempted to dismount a disk group that contains the Oracle Cluster Registry (OCR). The disk group cannot be dismounted until Cluster Ready Services (CRS) exits, because the disk group contains the OCR.

TYPE VARCHAR2(6) Redundancy type for the disk group:


  • HIGH

TOTAL_MB NUMBER Total capacity of the disk group (in megabytes)
FREE_MB NUMBER Unused capacity of the disk group (in megabytes)
HOT_USED_MB NUMBER Number of used megabytes in the hot region
COLD_USED_MB NUMBER Number of used megabytes in the cold region
REQUIRED_MIRROR_FREE_MB NUMBER Amount of space that is required to be available in a given disk group in order to restore redundancy after one or more disk failures. The amount of space displayed in this column takes mirroring effects into account.
USABLE_FILE_MB NUMBER Amount of free space that can be safely utilized taking mirroring into account and yet be able to restore redundancy after a disk failure
OFFLINE_DISKS NUMBER Number of disks in the disk group that are currently offline
COMPATIBILITY VARCHAR2(60) Minimum software version required for an ASM instance to mount this disk group
DATABASE_COMPATIBILITY VARCHAR2(60) Minimum software version required for a database instance to use files in this disk group
VOTING_FILES VARCHAR2(1) Indicates whether the disk contains voting files (Y) or not (N)


The GROUP_NUMBER, TOTAL_MB, and FREE_MB columns are only meaningful if the disk group is mounted by the instance. Otherwise, their values will be 0.