Dropping Disk Groups

Dropping Disk Groups

The DROP DISKGROUP statement enables you to delete an ASM disk group and optionally, all of its files. You can specify the INCLUDING CONTENTS clause if you also want to delete any files that might be contained in the disk group. The default is EXCLUDING CONTENTS, which provides syntactic consistency and prevents you from dropping the disk group if it has any contents

The ASM instance must be started and the disk group must be mounted with none of the disk group files open, in order for the DROP DISKGROUP statement to succeed. The statement does not return until the disk group has been dropped.

When you drop a disk group, ASM dismounts the disk group and removes the disk group name from the ASM_DISKGROUPS initialization parameter if a server parameter file is being used. If a text initialization parameter file is being used, and the disk group is mentioned in the ASM_DISKGROUPS initialization parameter, then you must remove the disk group name from the ASM_DISKGROUPS initialization parameter before the next time that you shut down and restart the ASM instance.

The following statement deletes dgroup1:

DROP DISKGROUP dgroup1;

After ensuring that none of the files contained in dgroup1 are open, ASM rewrites the header of each disk in the disk group to remove ASM formatting information. The statement does not specify INCLUDING CONTENTS, so the drop operation will fail if the disk group contains any files.

If you cannot mount a disk group but need to drop it, you can use the FORCE option of the DROP DISKGROUP statement. This command enables you to remove the headers on disks that belong to a disk group that cannot be mounted by any ASM instances as in the following example where disk_group_name is the name of the disk group:

DROP DISKGROUP disk_group_name FORCE

The disk group on which you perform this operation should not be mounted anywhere in the cluster. When you use the FORCE option, the ASM instance does not attempt to verify that a disk group is being used by another ASM instance in the same storage subsystem.