Not an answer to your question but:

You could look into getting rid of the database and instead setting up something similar to a mail folder, say Maildir. As this was designed for use with email which has many of the same traits of your problem it should work just fine. As many of the files will be cached in RAM doing this there should be no real performance penalty either due to disk access.

Maildir does not work on Win32 due to the filenames used, but something similar should be possible.

You could have a seperate folder for each client gaining you the security mentioned above. Backups would also become very simple. Of course if the daemons are on a different machine to the files then...

--tidiness is the memory loss of environmental mnemonics