A Critique of ANSI SQL Isolation Levels

ANSI SQL-92 defines Isolation Levels in terms of phenomena: Dirty Reads, Non-Repeatable Reads, and Phantoms. This paper shows that these phenomena and the ANSI SQL definitions fail to characterize several popular isolation levels, including the standard locking implementations of the levels. Investi...

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Bibliographic Details
Published in:arXiv.org 2007-01
Main Authors: Berenson, Hal, Bernstein, Phil, Gray, Jim, Melton, Jim, O'Neil, Elizabeth, O'Neil, Patrick
Format: Article
Language:English
Subjects:
Locking
Query languages
Online Access:Get full text
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Summary:ANSI SQL-92 defines Isolation Levels in terms of phenomena: Dirty Reads, Non-Repeatable Reads, and Phantoms. This paper shows that these phenomena and the ANSI SQL definitions fail to characterize several popular isolation levels, including the standard locking implementations of the levels. Investigating the ambiguities of the phenomena leads to clearer definitions; in addition new phenomena that better characterize isolation types are introduced. An important multiversion isolation type, Snapshot Isolation, is defined.
ISSN:2331-8422