Oracle Solution for Error ora-15027

ORA-15027: active use of diskgroup "string" precludes its dismount

What triggered the Error:

An ALTER DISKGROUP ... DISMOUNT command specified a diskgroup which had database client instances with open files in the diskgroup. Diskgroups cannot be dismounted until all open files in the diskgroup are closed by the database client instances.

What should we do to fix it:

Stop all clients that are using this diskgroup and retry the ALTER DISKGROUP ... DISMOUNT command. The V$ASM_CLIENT fixed view in an ASM instance provides a list of its active database client instances.