The Servlet specification defines session scope at the Web Application level, session information stored by one web application cannot be shared by other web applications even in the same enterprise application.WebSphere Application Server provides an IBM extension, that allows sharing the session information to be shared among web applications within an enterprise application. This option is offered as an extension to the application deployment descriptor.
In order to try this scenario i tried creating a Simple SessionContextSampleEAR. It has two .war files and each .war file has one servlet each. I am setting the session attribute in one servlet and accessing it in another and it works.
You can enalbe shared session context using RAD or IBM WAS Toolkit during the application assembly phase like this
Now if you check ibm-application-ext.xmi file in you .ear files META-INF folder you will see that value of sharedSessionContext attribute is set to true like this
<applicationext:ApplicationExtension xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:applicationext="applicationext.xmi" xmi:id="ApplicationExtension_1250896346141" sharedSessionContext="true">