You can generate a Java stack trace for debugging as described here if the Application Server is in verbose mode (see Enabling Verbose Mode):
The stack trace goes to the domain-dir/logs/server.log file and also appears on the command prompt screen.
If the -Xrs flag is set (for reduced signal usage) in the domain.xml file (under jvm-options), comment it out before generating the stack trace. If the -Xrs flag is used, the server might simply dump core and restart when you send the signal to generate the trace. For more about the domain.xml file, see the Sun Java System Application Server Enterprise Edition 8.1 2005Q2 Administration Reference.