We have been testing different VM's with our application deployed under JBoss. While using Blackdown we tried setting the initial heap size using -Xms 128M. After 30 minutes or so of activity the VM appears to stop garbage collecting and start grabbing huge chunks of memory until it finally dies. We are now using the IBM vm with the same argument with no problems. I'm happy enough with the IBM vm so I'm not too concerned about the Blackdown behavior...just curious if anyone else has seen this before.