Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu

Replica Freshness

  • Alan Fekete
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1367

Synonyms

Divergence control; Freshness control;Incoherency bounds

Definition

In a distributed system, information is often replicated with copies of the same data stored on several sites. Ideally, all copies would be kept identical, but doing this imposes a performance penalty. Many system designs allow replicas to lag behind the latest value. For some applications, it is acceptable to use out-of-date copies, provided they are not too far from the true, current value. Freshness refers to a measure of the difference between a replica and the current value.

Historical Background

The tradeoff between consistency and performance or availability is an old theme in distributed computing. In the database community, many researchers worked on ideas connected with explicitly allowing some discrepancy between replicas during the late 1980s and early 1990s. Early papers identified many of the diverse freshness measures discussed here, from groups at Princeton, Bellcore and Stanford [1, 10, 11]....

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Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.University of SydneySydneyAustralia

Section editors and affiliations

  • Bettina Kemme
    • 1
  1. 1.School of Computer ScienceMcGill Univ.MontrealCanada