Doctor of Philosophy(PhD) / Snapshot Isolation (SI) is a multiversion concurrency control that has been implemented by open source and commercial database systems such as PostgreSQL and Oracle. The main feature of SI is that a read operation does not block a write operation and vice versa, which allows higher degree of concurrency than traditional two-phase locking. SI prevents many anomalies that appear in other isolation levels, but it still can result in non-serializable execution, in which database integrity constraints can be violated. Several techniques have been proposed to ensure serializable execution with engines running SI; these techniques are based on modifying the applications by introducing conflicting SQL statements. However, with each of these techniques the DBA has to make a difficult choice among possible transactions to modify. This thesis helps the DBA’s to choose between these different techniques and choices by understanding how the choices affect system performance. It also proposes a novel technique called ’External Lock Manager’ (ELM) which introduces conflicts in a separate lock-manager object so that every execution will be serializable. We build a prototype system for ELM and we run experiments to demonstrate the robustness of the new technique compare to the previous techniques. Experiments show that modifying the application code for some transactions has a high impact on performance for some choices, which makes it very hard for DBA’s to choose wisely. However, ELM has peak performance which is similar to SI, no matter which transactions are chosen for modification. Thus we say that ELM is a robust technique for ensure serializable execution.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Thesis (M.Sc. (Hons.)) -- University of Western Sydney, 2001. / "Master of Science (Honours), Social Ecology, University of Western Sydney, Hawkesbury" Bibliography : leaves 227-231.

Univ., Diss.--Linz, 2002.

Thesis (M.S.)--University of Nevada, Reno, 2008. / "May, 2008." Includes bibliographical references (leaves 42-46). Online version available on the World Wide Web.

Thesis--University of London. / Without thesis statement. Bibliography: p. 169-176.

Thesis--University of London. / Without thesis statement. Bibliography: p. 169-176.

Thesis (Ph. D.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 104-113.

Thesis (Doctoral)--Universität Heidelberg, 1982.

Thesis (M.A.L.S.)--East Tennessee State University, 2003. / Vita. Includes bibliographical references (leaves 58-62). Original full text .pdf file available via the Internet. Requires Adobe Acrobat Reader software.