Monitoring With Visualvm Jvisualvm

First you have to enable jmx connection, explained at:
habilitar-acceso-jmx

Now you can start jvisualvm

tomcat@achtung:~/bin$ /usr/java/jdk1.6.0_23/bin/jvisualvm

and add a jmx conection: [ enter hostip:jmxport ]

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PermGen usage details:

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Note in this event, the heap has just been rezised: