Database transaction schedule: Difference between revisions

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Serializability is used to keep the data in the data item in a consistent state. It is the major criterion for the correctness of concurrent transactions' schedule, and thus supported in all general purpose database systems. Schedules that are not serializable are likely to generate erroneous outcomes; which can be extremely harmful (e.g., when dealing with money within banks).<ref name="Bernstein872">[[Phil Bernstein|Philip A. Bernstein]], Vassos Hadzilacos, Nathan Goodman (1987): [http://research.microsoft.com/en-us/people/philbe/ccontrol.aspx ''Concurrency Control and Recovery in Database Systems''] (free PDF download), Addison Wesley Publishing Company, {{ISBN|0-201-10715-5}}</ref><ref name="Weikum012">[[Gerhard Weikum]], Gottfried Vossen (2001): [http://www.elsevier.com/wps/find/bookdescription.cws_home/677937/description#description ''Transactional Information Systems''], Elsevier, {{ISBN|1-55860-508-8}}</ref><ref name="Herlihy1993">[[Maurice Herlihy]] and J. Eliot B. Moss. ''Transactional memory: architectural support for lock-free data structures.'' Proceedings of the 20th annual international symposium on Computer architecture (ISCA '93). Volume 21, Issue 2, May 1993.</ref>
 
If any specific order between some transactions is requested by an application, then it is enforced independently of the underlying serializability mechanisms. These mechanisms are typically indifferent to any specific order, and generate some unpredictable [[partial order]] that is typically compatible with multiple serial orders of these transactions. This partial order results from the scheduling orders of concurrent transactions' data access operations, which depend on many factors.
 
Serializability is used in concurrency control of databases,<ref name="Bernstein872">[[Phil Bernstein|Philip A. Bernstein]], Vassos Hadzilacos, Nathan Goodman (1987): [http://research.microsoft.com/en-us/people/philbe/ccontrol.aspx ''Concurrency Control and Recovery in Database Systems''] (free PDF download), Addison Wesley Publishing Company, {{ISBN|0-201-10715-5}}</ref><ref name="Weikum012">[[Gerhard Weikum]], Gottfried Vossen (2001): [http://www.elsevier.com/wps/find/bookdescription.cws_home/677937/description#description ''Transactional Information Systems''], Elsevier, {{ISBN|1-55860-508-8}}</ref> transaction processing (transaction management), and various [[Database transaction|transactional]] applications (e.g., [[transactional memory]]<ref name="Herlihy1993">[[Maurice Herlihy]] and J. Eliot B. Moss. ''Transactional memory: architectural support for lock-free data structures.'' Proceedings of the 20th annual international symposium on Computer architecture (ISCA '93). Volume 21, Issue 2, May 1993.</ref> and [[software transactional memory]]). Serializability is considered the highest level of [[Isolation (database systems)|isolation]] between [[Database transaction|transactions]], and plays an essential role in [[concurrency control]].
 
'''Serializability theory''' provides the formal framework to reason about and analyze serializability and its techniques.
 
====Conflicting actions====