Hi Jim, I'm wondering if you can still remember the rational behind the cache code at around lines 355-387 of: http://svn.zope.org/Zope/trunk/lib/python/Shared/DC/ZRDB/DA.py?rev=68158&vie... This code is pretty old (checked in 5th Dec 1997) but has started causing a few people problems under high load: http://mail.zope.org/pipermail/zope-db/2006-September/004684.html http://www.zope.org/Collectors/Zope/2212 In particular: - in line 368, why is len(cache)>max_cache/2 used as a trigger to start cache clearing? (the /2 in particular) - does it matter that IOBTree.Bucket has gone away and that tcache is now a simple dictionary? It certainly seems to make the keys.reverse() on line 370 superfluous and the keys[-1]<t on line 371 less reliable. More generally, do you or does anyone else have any attachment to this code or would anyone mind if I ripped it out and replaced it with something simpler, with more comments and unit tests? cheers, Chris -- Simplistix - Content Management, Zope & Python Consulting - http://www.simplistix.co.uk