You can generate a Java stack trace for debugging as described here:
If the -Xrs flag is set (for reduced signal usage) in the server.xml file (under <JVMOPTIONS>), comment it out before generating the stack trace. If the -Xrs flag is used, the server may simply dump core and restart when you send the signal to generate the trace.
The stack trace goes to the system log file or to stderr based on the LOG attributes in server.xml.
For more information about the server.xml file, see the Sun Java System Web Server 6.1 SP7 Administrator’s Configuration File Reference.