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A database session is sequence of interactions between a client and a database server. The session captures the state of the client’s in-flight SQL commands.
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Session state may contain database objects, such as temporary relations, which are accessible only within the session. For efficiency, some database engines maintain session state per connection rather than per client. In this case, it is called connection state.
A client expects to see the effects of its previous updates to the database. This concept is called session consistency [1] and is illustrated in the following example. A client issues a transaction to buy a book. Then, it sends a subsequent transaction to see the list of ordered books. Session consistency requires the list to contain that book. Session consistency is trivial to implement in a centralized database system, but becomes harder in a distributed database system.
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Recommended Reading
Daudjee K. and Salem K. Lazy database replication with ordering guarantees. In Proc. 20th Int. Conf. on Data Engineering, 2004, pp. 424–435.
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© 2009 Springer Science+Business Media, LLC
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Elnikety, S. (2009). Session. In: LIU, L., ÖZSU, M.T. (eds) Encyclopedia of Database Systems. Springer, Boston, MA. https://doi.org/10.1007/978-0-387-39940-9_667
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DOI: https://doi.org/10.1007/978-0-387-39940-9_667
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