Thanks to everyone for all the hints. I still don't understand all the ins and outs, but this really helps me. In my case this is a statically-configured system, i.e. I set it up months or years ago with a particular max memory and a particular total logical memory, and I might make changes only very rarely, and when I do I will tend to reboot the machine soon afterwards. This machine is dedicated to running ASE. My puzzle was why, out of the blue, did this system start experiencing memory-related issues. Especially when other ASE systems of mine run fine with a nearly identical configuration. Anyway, since my last post I have played with the memory settings, and ended up reducing total logical memory by 1GB and max memory by 2GB, and the problems seem to have stopped. For now I'm just going to go with that and maybe I'll figure it all out later. (Someone hinted to me that the culprit could be the ZFS cache...)
Thanks.
- John.