Cyrus 2.1.15 database files

[Patrick Goetz]

OK, no response on the "unable to update user.seen database files" for
some users question I asked earlier, so let me try something else.

Is there any documentation on the cyrus database files?  For example,
since /var/lib/cyrus/user/t/this_user.seen seems not to be keeping track
of what messages this_user has looked at, can I just delete this file and
assume that cyrus will create another one?

Which database files do what?

Which ones (if any) can be safely deleted, since they will be
automatically regenerated (with, of course, a loss of information)?

Which database files must be backed up in order to fully restore a cyrus
mail system when a system is re-installed?

I looked at the wiki and have read the documentation (I think), and I
can't find an answer to any of these questions.