Cause: The filename supplied as a parameter to the ALTER DATABASE BACKUP
CONTROLFILE command or to cfileSetSnapshotName matches the
name of the specified currently mounted control file.
Action: Retry the operation with a different filename.
Related posts
ORA-00243 Failed to expand control file filename section by %s records
ORA-00243 Failed to expand control file filename section by %s records
Oracle Database Internal Mechanism 