As people already noted, this is essentially impossible for a bunch of reasons. ...but... You could add to Zope some sort of access counters on all objects. You could reset this on a live site, twiddle your thumbs for a week, then dump those counters. Objects with the smallest counters are clear candidates for removal but you would have to make the decision with your brain or other equivalent thought-organ. No automated process can remove all dead objects safely in a system like Zope. There would be a fairly large performance impact if those counters live in the objects since then the assumption the object DB is primarly a read-only resource would be false. However you could keep it in-core since the counters would be just a guide and it wouldn't be much larger than the DB index. In fact I bet you could attach such a sytem to the ZODB index logic pretty easily... Hmm... I think I'm talking beyond my knowledge. I think I'll shut up now.