6 Frequently Asked Questions

This chapter contains frequently asked questions and answers about Java Mission Control.


Java Mission Control requires a commercial license for use in production. To learn more about commercial features and how to enable them please visit http://www.oracle.com/technetwork/java/javaseproducts/.

The following issues sometimes arise:

Issue 1   I cannot connect to the JVM. What could be the problem?

Consider the following:

  • Are you using the correct protocol?

    Ensure that you are using the same version of the JVM that you want to monitor as is being used by the JVM running the JMC client.

    The format of the service URL is:


  • Are the correct ports opened?

    Note that running JMX over RMI requires two ports and that one of the ports will not be known beforehand.

  • Is the communication caught in a firewall?

    For more information, see "Java Mission Control Communications" in the Introduction to Java Mission Control on the Oracle Technology Network.

Issue 2   When attempting to connect to a JVM, I get a stack trace indicating that the JVM attempts to communicate with a strange IP or host name. What does this mean?

Sometimes RMI can have a problem determining which address to use. This can happen because of any of the following:

  • There are access restrictions in the Security manager.

  • The machine is multihomed and RMI is selecting the wrong interface.

  • There is a mis-configured hosts file or a number of different network related configuration problems.

If all else fails, you can try specifying the java.rmi.server.hostname system property. Note that this can affect applications running on the JVM.

Issue 3   I am getting exceptions during startup about classes not being found. What is wrong?

Ensure that you are using JAVA_HOME/bin/jmc to start the JMC client.

Issue 4   Why does Java Mission Control fail to find any local JVMs?

Consider the following:

  • Make sure that you are using JAVA_HOME/bin/jmc to start the JMC client.

  • If you are running JMC from Eclipse, make sure that Eclipse is running on a JDK (not JRE).

  • Make sure that there is a directory named hsperfdata_username in the system's tmp directory, that it is writable by the user running JMC, and that the file system supports access control lists (ACLs).

Issue 5   How do I connect to JBoss?

Before starting JMC, you need to add the -Xbootclasspath/a option to the -vmargs section of the jmc.ini file. The value for this option (after a colon) should be set to the extended classpath that is generated by JBoss's jconsole.bat file (for this, add @echo on to the file and run it).