Network Latency Optimizations in Distributed Database Systems

The advent of high-speed networks will enable the deployment of data-server systems currently used in localarea networks, over wide-area networks. The users of these systems will have the same high expectations with respect to performance parameters such as the transaction throughput, response time and system reliability as in the case of local-area networks. Thus, it is important to study the performance of existing distributed database protocols in the new networking environment, identify the performance bottlenecks and develop protocols that are capable of taking advantage of the high speed networking technology. As a first step, in this paper we examine the scalability of the server-based two-phase locking (s-2PL) protocol, and discuss three optimizations which allow the s-2PL protocol to be tailored for high-speed wide-area network environments where the size of the message is less of a concern than the number of rounds of message passing. These optimizations, collectively called the group two-phase locking (g-2PL) protocol, reduce the number of rounds of message passing by grouping lock grants, client-end caching and data migration. In a simulation study, 20-25% improvement in the response time of the g-2PL protocol over that of the s-2PL protocol was observed.