ASM_DISKSTRING specifies an operating system-dependent value used by Oracle ASM to limit the set of disks considered for discovery.

Property Description

Parameter type



ASM_DISKSTRING = discovery_string [, discovery_string ] ...

Default value

The null string; Oracle Automatic Storage Management discovery finds all disks in an operating system-specific location to which the Oracle Automatic Storage Management instance has read/write access.



Modifiable in a PDB




Oracle 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.


This parameter may only be specified in an Oracle Automatic Storage Management (Oracle ASM) instance.

When a new disk is added to a disk group, each Oracle ASM 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 Oracle ASM 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.

See Also:

Oracle Automatic Storage Management Administrator's Guide for more information and examples of using this parameter