All, As a coincidence, that hang of Zope I mentioned in a message I posted yesterday has happened again today (second time), after a planned reboot. So here is a completely different issue from the memory one we've been discussing today. There was other weirdness (for whatever reason _mysql could not find libmysqlclient_r.so.15 on some restart attempts), but here is something that seemed to occur consistently while Zope was unresponsive: On FreeBSD 5.4, with zserver-threads set to the default 4, there were seven Zope threads with the following states (CPU use is 0% and memory use is well below the maximum, pretty much where it is at after a normal fresh Zope restart): select ksesig kserel kqread kqread kqread kqread When Zope is operating normally and idle, I generally only see the three top threads, and when serving pages, I rarely see more than three threads; one actually often disappears and I only see two, one in the RUN state. I know that the kqread state has to do with the kqueue or kevent system call, and assume that Zope being in that waiting state for a long time is abnormal. Asking here in case someone has seen this behavior before and knows what might be the cause. As for the last and only other time this happened, Zope regained normal behavior by itself after a little while (in the order of half an hour). I don't see anything abnormal in the event log (other than the _mysql issue I mentioned above), and while stuck, requests do not register in the Z2.log. Browsers do get a connection because they state "waiting for..." but they do not receive anything, not even headers. After a fresh restart, I could get Zope to respond to a relatively benign request (the top level ZMI page), while there were only three Zope threads, but if asking for more, Zope would quickly get to the unresponsive state described above. We're thinking that we may be having underlying OS issues and will probably ask on a FreeBSD list and/or upgrade FreebBSD and hope that helps, but I'm asking here first just in case that this pattern of behavior was observed and resolved before. Cheers, Jean