Cause: An attempt was made to ADD to a diskgroup a disk that was already part of another diskgroup, or an attempt was made to DROP / OFFLINE / ONLINE / CHECK a disk that was not part of the specified diskgroup. See the solution below.
Error solution: For ADD, check the path specifier for the disk. If it is certain that the disk is not in use by another diskgroup, the FORCE option may be used to override this check. For the other commands, check the name of the specified disk.
Database version: Oracle 11g Release 2 (11.2)