Syntax:ASM_DISKGROUPS = diskgroup [, diskgroup ]…
Default:There is no default value.
Range:Comma-separated list of strings, of up to 30 characters
Rac:Multiple instances can have different values. Different nodes might see
the same disks under different names; however, each instance must be
able to use its ASM_DISKSTRING to discover the same physical media
as the other nodes in the cluster.
Notes:ASM_DISKSTRING specifies an operating system-dependent value used by Automatic Storage Management to limit the set of disks considered for discovery. When a new disk is added to a disk group, each Automatic Storage Management instance that has the disk group mounted must be able to discover the new disk using the value of ASM_DISKSTRING.In most cases, the default value will be sufficient. Using a more restrictive value may reduce the time required for Automatic Storage Management to perform discovery, and thus improve disk group mount time or the time for adding a disk to a disk group.A "?" at the beginning of the string gets expanded to the Oracle home directory.Depending on the operating system, wildcard characters can be used.It may be necessary to dynamically change ASM_DISKSTRING before adding a disk so that the new disk will be discovered.An attempt to dynamically modify ASM_DISKSTRING will be rejected and the old value retained if the new value cannot be used to discover a disk that is in a disk
group that is already mounted.