 The file access enqueue could not be obtained for a file specified in a backup, copy or restore operation. If the enqueue type shown is SHARED, then the file is the input file for a backup or copy. If the type is EXCLUSIVE, then the file is the output file for a datafile copy or restore which is attempting to overwrite the currently active version of that file. In this case, the file must be offline or the database must be closed. If the type is read-only, then you are attempting to back up or copy this file while the database is in NOARCHIVELOG mode.