|| Confirm that the file mentioned is not a repeat of a file already mentioned in the command. If they are different files then omit the earlier backup. If they are members of the same log, insure they are in the same group file specification. If this message appears because of a duplicate control file, check the control_files parameter in the init.ora file and see if a file is specified more than once. If all files names appear to be unique, check to make sure that the actual control files themselves are unique. For example, in UNIX check for a symbolic or a hard link to another control file in the list.