I have a Java web app running on tomcat on Linux Red hat on an Intel box with 2 GR of RAM. We're having trouble because the application intermittently hangs. The threads never go anywhere near the max. The CPU usage never goes above 2%. The memory does not get used up. Nevertheless, the tomcat server hangs. Obviously this could be a deadlock. Or, it could be connected to the fact that the application uses a third-party tool, which requires a JDBC connection to a middleware network program on the database server, called Omnidex. What I need to know is how I can go about figuring out what's going wrong. In the short term if there's something I can do in tomcat logging or tracing, I'd like to know. Also, I'm interested in suggestions for software to purchase that can do a better job of analyzing what is going on in the JVM to track down what is going on. The problem appears and then goes way and then reappears. It is clearly linked to number of users, but the problem appears with only 18 users at a time. So I know that none of you can tell me what's wrong. I'm looking for where to start doing diagnostics. I have a whole book on Tomcat development and it has not a single section on tomcat problem solving. Thanks.