My Oracle Support Banner

How To Drop and Recreate ASM Diskgroup (Doc ID 563048.1)

Last updated on FEBRUARY 11, 2024

Applies to:

Oracle Database - Standard Edition - Version to [Release 10.2 to 11.2]
Oracle Database - Enterprise Edition - Version to [Release 10.2 to 11.2]
Oracle Database Cloud Schema Service - Version N/A and later
Gen 1 Exadata Cloud at Customer (Oracle Exadata Database Cloud Machine) - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Information in this document applies to any platform.


This article describe how we can drop and recreate ASM diskgroup when its not possible to perform this through SQL command.

When a member disk in external redundancy diskgroup is no longer present (or destroyed beyond repair) and you want to drop the diskgroup completely and recreate it or add the disks of the diskgroup to other diskgroups. The diskgroup can not be mounted, because one of the disks is missing, hence the "drop diskgroup" command will not work.

In 10g you can use a workaround by erasing the header of the disk using the dd command.

In 11g, the diskgroup can be dropped when its dismounted with FORCE option especially for normal and high redundancy diskgroups:

Oracle� Database Storage Administrator's Guide - 11g Release 1 (11.1)
Administering ASM Disk Groups
Dropping Disk Groups

Erasing the header using "dd" command is very dangerous operation and need to be done under support supervision and when it confirmed by support that fixing the header is impossible.

In all cases and before the erasing operation you should gather the following information:

1. alert.log file from all ASM instances going back to last successful mount for diskgroup.
2. OS logs.
3. Backup disk header for all member disks in diskgroup:


To view full details, sign in with your My Oracle Support account.

Don't have a My Oracle Support account? Click to get started!

In this Document

My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts.