If single instance of the server hosts multiple sites, does each site start its own jvm (java virtual machine) or are sites more like logical entities within the server so they run in the same JVM instance, kind of like in bea weblogic that can hosts multiple ‘sites’ in the same jvm instance ?? I am J2EE consultant and I have been asked to investigate the perfomance impact of having multiple sites on the same instance and I am starting by trying to understand if a ‘site’ is a logical entity within a JVM instance. Any pointers will be appreciated. I have been asked this question from a purely J2EE perfomance point of view and I know that running multiple JVMs can be a drain. Most analysts in our shop who deal with this product see it from a functional point of view and I have to understand it from a J2EE server point of view.