If an IIS application needs to rely on the session state, then you should try to avoid putting large data in the session object and session states. Session tracking maintains information about a set of requests that are issued by a single client. Remember that the Sessions in IIS are persistent, and the memory allocated to the sessions are not freed until the session has been terminated or timed-out. If many concurrent users are using the application, the server’s resources could become depleted, and performance could be affected. Therefore you should try to avoid putting large data in the Session object and Session states to save on resources.