Isolation of data in a session is the trickiest part of session management. A session may constitute of multiple requests. Transactions with appropriate isolation levels are used for data isolation in a request.
Martin Fowler in his book Patterns of Enterprise Application Architecture (P of EAA) uses two terms – system transaction and business transaction. A session can use one or more business transactions. A request is usually executed as one or more system transactions. A business transaction may require execution of multiple requests or in other words may consists of multiple system transactions. A […]