6 Frequently Asked Questions

6.1.1 I cannot connect the JMC Client 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 Java JVM that you want to monitor as is being used by the Java JVM running the JMC client.

  The format of the service URL is:

  service:jmx:rmi:///jndi/rmi://<hostname>/jmxrmi

• 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.

6.1.2 When attempting to connect the JMC client to a JVM, I get a stack trace indicating that JMC 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 misconfigured 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 in the Java JVM.

6.1.3 I'm 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.

6.1.4 Why Java Mission Control does not find any local JVMs?

Ensure that you are using JAVA_HOME/bin/jmc to start the JMC client. Make sure that there is a directory named hsperfdata_USER in your tmp directory, where USER is your login name. Make sure that the user has write permissions for this directory. Also make sure that you are using a file system that supports access control lists (ACLs).