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.
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.
Retry the operation with a different filename.
Try the following links for this error:
http://docs.oracle.com/cd/E16655_01/server.121/e26079/e0.htm
https://community.oracle.com/message/4538468
https://community.oracle.com/message/9532988
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