FWIW, I just did a little monitoring with JConsole with my current development setup: Eclipse, Jetty, Cayenne 3.0M6, Tapesty 5.1, MySQL. This new application I'm working on sounds similar to yours. Fairly lightweight. After everything loaded in, I was using 20-21 MB of memory and it stayed steady, even after doing about 100 queries in Cayenne (I tend to pull back 1-7 records per set-of-queries, but closer to 2-3 on average). I'm using session-based data contexts and on-demand data contexts. The memory footprint was fine and I'm not caching (I go get fresh data every query). I'm not sure why you are seeing the anomaly you are seeing unless you just need a bit more RAM for Tomcat to be stable.
mrg
