From my understanding, it should work like this. When you first bring up the app server, there are no connections. The first app that needs a connection causes 10 (min-pool-size) connections to be created. If additional connections are needed, up to max-pool-size connections will be created. If more than min-pool-size connections are made, and any of them are idle for more than idle-timeout-minutes, then they are closed, but there will always be at least min-pool-size connections.