> > The SWEEP is quite fast if there is no 'garbage' in the database.
>
> Anyway, if this statement that sweep touches every single record of the
> database is true(?) then sweep must do quite a job.
> Any known plans for FB to optimize this garbage collection?

Probably not, because it would require some extra bookkeeping
that would slow down regular operations. Besides, you do not need
to use sweep with most databases, because old versions are removed
by cooperative garbage collection, and OIT can be stuck also
under some special conditions only (like rolback after _huge_ update,
or failed two-phase commit).

Ivan
http://www.volny.cz/iprenosil/interbase