Diagnostic commands can also be invoked by overriding the default behavior of the SIGQUIT process signal. Recollect from Chapter 4 that the default behavior of a JVM receiving a SIGQUIT is to write a thread dump containing the current state of all the threads to the console. One way of sending a SIGQUIT signal to the JVM process is to press Ctrl + Break (Windows), or Ctrl + \ (Linux), in the shell where the Java process was started. On *NIX-systems, executing kill -3 <PID> or kill -QUIT <PID> from a shell is an alternative way of issuing a SIGQUIT to a process with a given ID.

To override the SIGQUIT behavior of JRockit with a custom command sequence; put the list of commands to be executed in a plain text file and name it ctrlhandler.act. The file needs to be placed into the lib folder of JRockit distribution or the current directory of the JVM process. The presence of a crtlhandler.act file overrides the behavior of the SIGQUIT signal and makes it execute...