Triggering a Thread Dump

There are two methods for triggering a Java thread dump. One method is to send the Java virtual machine (UVM) an operating-environment signal (SIGQUIT). The other method is the programmatic use of tools that are included in the Java Development Kit (JDK).

Send the JVM an Operating-Environment Signal

This method varies by operating environment. Thread dumps that are triggered by the operating environment are written to the standard output (STDOUT) file. You can also trigger multiple dumps, which are all written to the stdout file.

For Microsoft Windows environments, the Java application must run in a command window with STDOUT redirected to a file. When you want to produce a thread dump, simply press CTRL-Break in that window to send the SIGQUIT signal.

• UNIX Operating Environments
  • ​​​​​​Use the kill command to send the JVM process a SIGQUIT signal, as shown in the following example:
    
       kill -3 process_id
    
    Note: This command does NOT kill the process; it simply instructs the JVM to generate the thread dump and continue.
  • Locations for your UNIX thread dumps:
    • Hotspot and Zulu JVMs write the thread dump to the stdout file.
    • IBM JVMs write thread dumps to individual javacore.* files.
  • Windows Operating Environments

    You need to install a JDK to trigger thread dumps in Windows environments. The JDK includes the following commands that you can use:

    • jstack:
      jstack -l pid file-path
    • jvisualvm:
      
      For details about this command, see SAS Note 42373, "Using the jvisualvm tool to remotely monitor a Java virtual machine."