Don't lock database when updating it

[spwhitton]

A Debian user makes the following suggestion:

Since the db update will effectively replace the db when done, wouldn't 
it make sense to copy the db to another file, do the update on that file 
and then over-write the original file at the end of the process, thus 
minimising the time the file needs to be locked?

The advantage of this is that it would permit using the old database while the update process is running.