You can use JConsole (Sun, http://java.sun.com/javase/6/docs/technotes/guides/management/jconsole.html) or visualvm (https://visualvm.dev.java.net/) to monitor Oracle Application Serveror standalone OC4J standalone.

See also Metalink Note 443506.1.

• Add "-Dcom.sun.management.jmxremote" to your JVM.

For Application Server 10.1.3.x goto $ORACLE_HOME/opmn/config.

Edit opmn.xml. Add this to the process-type/start-paramters/java-options of the "home" or "oc4j-soa" or ...
Restart Application Server

For OC4J standalone ...

For Application Server 11g (Technology PreviewTP3 or TP4)

Go to your $JDEV_USER_DIR/system11.1.1.0.22.48.95/o.j2ee/embedded-oc4j\bin
Edit the startsoa(.bat): add "-Dcom.sun.management.jmxremote" to the JAVA_VM paramter
Start the server with this script and from within the JDeveloper 11g.

• Start JConsole and select the local process with "oc4j..."

JConsole Sceens:

• Start visualvm and select on the left side the process with "oc4j.jar"

visualvm Screen: