On rare occasions a FATMEN catalogue may become corrupted. To recover, one can simply restore the most recent backup copy and reapply all journal files since the time of the backup. (Simply copy or move them from the done directory to the todo directory. The time stamp in the filenames will ensure that they are processed in the correct order).
Alternatively, one can attempt to 'repair' a catalogue. This may be necessary if the corruption is not noticed for some time. This can happen if a systematic check of the catalogue is not made before every backup as corruption typically affects only a few entries which may well not be accessed for some time.
Repairing a corrupted catalogue consists of the following steps: