Restoring a backup using a .DAT file

If the .DAT file was copied while Ensemble was running, it could be corrupt (there could be blocks that were written in memory but not yet to disk). The only reliable way to use a .DAT file as backup is when the file was copied while Ensemble was down, or when the file was dismounted. (the .lck file should not be present in the same directory as the .DAT file)
The good thing about a backupped .DAT file is that you can mount it as a new database, and copy stuff from it while the rest is still running as is.