The Application_OnEnd function is called when the application ends, which occurs when IIS shuts down. It removes the Application object from memory. The Application object is not persistent, meaning that any data stored in the Application object is lost when IIS shuts down.
Set Application("RenderingApplication") = Nothing
This function is not called when an individual user session ends; that is, it is unaffected by events such as time-outs and user-requested exits.