| With the development of database technology and network technology, people are paying more attention on distributed database system. Because of the characteristic of distribution and logic of the distributed database, how to ensure the atomicity of distributed transaction commit, is more concerned by distributed database system. Three-phase commit protocol is advanced based on the two-phase commit protocol. On the basis of ensuring the atomicity of the distributed transaction commit, three-phase commit protocol has in partially improved the shortcomings of the two-phase commit protocol which is easy to blocking, and enhanced system performance and system resource utilization rate. But the three-phase commit protocol has its own inherent disadvantages: a larger network communication. Therefore, how to reduce the three-phase commit protocol's network communication has an important significance to the distributed database system.First, this paper introduces the common transaction commit protocol, and gives detailed descriptions of several three-phase commit protocols: proxy based three-phase commit protocol (P3PC), heart beat based three-phase commit protocol (HBB-3PC), and redundancy based three-phase commit protocol (R3PC). This paper has analyzed the advantages and disadvantages of these three commit protocol.Then, on the basis of R3PC, in allusion to the coordinator's blocking, for the purpose of improving the selection of the new efficiency coordinator; this paper ameliorates the three-phase commit protocol and puts forward two new coordinator selection algorithms: the counter selection algorithm and the TTL selection algorithm. At the same time, this paper analyzes the advantages and disadvantages of these two algorithms.Finally, this paper analyzes the failure of the distributed database system and gives a common recovery strategy. And it describes how the new coordinator to supersede the old coordinator'work after the failure occurring. |
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