I read Marty Hall's SCWCD Exam review in SCWCD links in javaranch site
I read the following paragraph in page 15
� Presumably they mean "in a distributed Web app." The point is that the servlet context and sessions are guaranteed to be shared in a Web app running on a distributed (clustered) server. But, listener instances have no such guarantee, so they cannot store data in their instance variables (fields). Same goes for instance variables of servlets: not safe in distributed apps.
BUT AS I know that
In the case of a web application marked "distributed " in its deployment descriptor, there will be one context instance for each virtual machine. In this situation, the context cannot be used as a location to share global information (because the information won 't be truly global). Use an external resource like a database instead.
I think the sevlet context can not be shared in clustered environment