A session bean  is created by a client and usually exists only for the duration of a single client/server session. 
A session bean performs operations, such as calculations or accessing a database, for the client. While a session 
bean may be transactional, it is not recoverable should a system crash occur. Session bean objects can be either 
stateless or they can maintain conversational state across methods and transactions. If they do maintain state,
 then the EJB container manages this state if the object must be removed from memory. However, the session bean
 object itself must manage its own persistent data.