Synonyms
Conflict serializability; Isolation; Locking protocol; Pessimistic scheduler
Definition
A locked transaction is a transaction which, in addition to read and write actions, contains lock and unlock operations to the data items. Lock and unlock operations enable a database system to control the order of read and write actions of a concurrent set of transactions. A locking policy is a set of rules which restrict the possible ways to introduce lock and unlock operations into a transaction. A locking policy is safe, if, whenever all the transactions conform to the policy, any history of the transactions is guaranteed to be serializable. Two-Phase Locking is a safe locking policy which is based on the simple rule saying a transaction is not allowed to further lock a data item once it has already unlocked some data item.
This is a preview of subscription content, log in via an institution.
Buying options
Tax calculation will be finalised at checkout
Purchases are for personal use only
Learn about institutional subscriptionsRecommended Reading
Agrawal D, Abbadi AE. Constrained shared locks for increased concurrency in databases. J Comput Syst Sci. 1995;51(1):53–63.
Bayer R, Heller H, Reiser A. Parallelism and recovery in database systems. ACM Trans Database Syst. 1980;5(2):139–56.
Bernstein PA, Newcomer E. Principles of transaction processing for systems professionals. San Francisco: Morgan Kaufmann; 1996.
Bernstein PA, Shipman DW, Wong WS. Formal aspects of serializability in database concurrency control. IEEE Trans Softw Eng. 1979;SE-5(3):203–15.
Boral H, Gold I. Towards a self-adapting centralized concurrency control algorithm. In: Proceedings of the ACM SIGMOD International Conference on Management of Data; 1984. p. 18–32.
Eswaran KP, Gray JN, Lorie RA, Traiger IL. The notion of consistency and predicate locks in a database system. Commun ACM. 1976;19(11):624–33.
Gray J, Reuter A. Transaction processing: concepts and techniques. San Francisco: Morgan Kaufmann; 1993.
Lausen G. Concurrency control in database systems: a step towards the integration of optimistic methods and locking. In: Proceedings of the ACM Annual Conference; 1982. p. 64–68.
Papadimitriou CH. The serializability of concurrent database updates. J ACM. 1979;26(4):631–53.
Salem K, Garcia-Molina H, Shands J. Altruistic locking. ACM Trans Database Syst. 1994;19(1):17–165.
Shasha D. Database tuning – a principled approach. Englewood Cliffs: Prentice-Hall; 1992.
Weikum G, Vossen G. Transactional information systems – theory, algorithms, and the practice of concurrency control and recovery. San Francisco: Morgan Kaufmann; 2002.
Author information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Section Editor information
Rights and permissions
Copyright information
© 2018 Springer Science+Business Media, LLC, part of Springer Nature
About this entry
Cite this entry
Lausen, G. (2018). Two-Phase Locking. In: Liu, L., Özsu, M.T. (eds) Encyclopedia of Database Systems. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-8265-9_832
Download citation
DOI: https://doi.org/10.1007/978-1-4614-8265-9_832
Published:
Publisher Name: Springer, New York, NY
Print ISBN: 978-1-4614-8266-6
Online ISBN: 978-1-4614-8265-9
eBook Packages: Computer ScienceReference Module Computer Science and Engineering