Degree Name

Master of Computer Science by Research


Computer Science Department - Faculty of Informatics


In this thesis, concept of database concurrency control, computational models of database transaction, the correct criterias of concurrent execution of transactions and concur- rency control algorithms such as two phase locking, serialization graph testing, Snap- shot Isolation are reviewed. A graph based mechanism is proposed for preserving Snapshot Isolation protocol(SI) serializable at run-time. Firstly, we present Dynamic Managed Snapshot Isolation Serialization Graph(called DSISG). By using this mecha- nism, non-serializable transactions under Snapshot Isolation protocol can be detected at run-time. Secondly, in order to guarantee the effectivity of DSISG, a new model of database transaction(segmented transaction model) is proposed. Thirdly, an algorithm of managing a hierarchical structured acyclic graph is presented. The run-time charac- terzing of non-serializable transaction under Snapshot Isolation protocol will be more effcient when this hierachical graph structure is applied to DSISG. We also summarize the contributions of this thesis and formulate some open problems.

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