In
computer science
Computer science is the study of computation, automation, and information. Computer science spans theoretical disciplines (such as algorithms, theory of computation, information theory, and automation) to practical disciplines (includi ...
, in the field of
database
In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases s ...
s, write–write conflict, also known as overwriting
uncommitted
''Uncommitted'' is XIA's first single. It consists of title track "Uncommitted" and an oriental version of the title song of his first Korean studio album ''Tarantallegra'', which was released earlier in 2012. Both songs on this single are sung ...
data is a computational anomaly associated with interleaved execution of
transactions.
Given a
schedule S
note that there is no read in this schedule. The writes are called ''blind writes''.
We have a ''lost update''. Any attempts to make this schedule serial would give off two different results (either T1's version of A and B is shown, or T2's version of A and B is shown), and would not be the same as the above schedule. This schedule would not be
serializable.
Strict 2PL overcomes this inconsistency by locking T1 out from B. Unfortunately,
deadlock
In concurrent computing, deadlock is any situation in which no member of some group of entities can proceed because each waits for another member, including itself, to take action, such as sending a message or, more commonly, releasing a loc ...
s are something Strict 2PL does not overcome all the time.
See also
*
Concurrency control
In information technology and computer science, especially in the fields of computer programming, operating systems, multiprocessors, and databases, concurrency control ensures that correct results for concurrent operations are generated, while ...
*
Read–write conflict
*
Write–read conflict
References
{{DEFAULTSORT:Write-write conflict
Data management
Transaction processing