Encyclopedia of Database Systems

2009 Edition
| Editors: LING LIU, M. TAMER ÖZSU

Weak Consistency Models for Replicated Data

  • Alan Fekete
Reference work entry
DOI: https://doi.org/10.1007/978-0-387-39940-9_1537
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Synonyms

 Weak memory consistency;  Copy divergence

Definition

Some designs for a distributed database system involve having several copies or replicas for a data item, at different sites, with algorithms that do not update these replicas in unison. In such a system, clients may detect a discrepancy between the copies. Each particular weak consistency model describes which discrepancies may be seen. If a system provides a weak consistency model, then the clients will require more careful programming than otherwise. Eventual consistency (q.v.) is the best-known weak consistency model.

Historical Background

In the late 1980s and early 1990s, replication research focused on systems that allowed replicas to diverge from one another in controlled ways. Epidemic or multi-master algorithms were introduced in the work of Demers et al. [4]. These researchers identified the importance of session properties [8], which ensure that clients see information that includes changes they could...

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Recommended Reading

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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Alan Fekete
    • 1
  1. 1.University of SydneySydneyAustralia