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 Automatic Storage Management 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 Automatic Storage Management instance that mounted the disk group

  • UNKNOWN - Automatic Storage Management instance has never attempted to mount the disk group

  • DISMOUNTED - Disk group was cleanly dismounted by the Automatic Storage Management instance following a successful mount

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

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)
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


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.