I agree with Gabriel that info center is a very helpful place to learn about anything you want and this is a brief about dump name space in WAS!
Dump Name Space
J2EE environments and applications depend on a service called the Java Naming and Directory Interface (JNDI) service. The JNDI service provides a central repository for the addresses of all the J2EE resources — EJBs, Java Message Service (JMS) resources, and Java Database Connectivity (JDBC) resources, and so on. If you start receiving a “name not found” exception, it’s usually a clue that some issue exists with how or whether the resource is registered in the JNDI name space.
IBM ships WebSphere with a utility you can use to dump your JNDI name space. To invoke the dumpnamespace utility (.bat on Windows and .sh on Unix), go to the \bin directory, and run
dumpnamespace