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Performance Modeling of an Enhanced Optimistic Locking Architecture for Concurrency Control in a Distributed Database System

Optimistic methods of concurrency control are gaining popularity. This is especially true with the resurgence of mobile and distributed databases during the last decade, which inherently rely on optimistic techniques to improve availability and performance of the distributed database systems. A key problem with optimistic techniques is that they do not perform well in highly conflict prone environments. Pessimistic techniques, especially locking, perform much better under these circumstances. In this research effort, the authors explored a hybrid technique called optimistic locking architecture that provides locking for high conflict data items and optimistic access for the rest. The model uses self-tuning that does not require the transaction manager, the transaction or the user to incorporate any additional knowledge or to specify which data items or transactions are optimistic. Rather, the system uses a data structure called lock buffer to maintain optimal level of locks in the system. The empirical results obtained show that the performance of optimistic concurrency control techniques can be significantly improved by using a relatively small lock buffer. The analysis of the results also show improved performance degradation which is suitable to the distributed database environment. ACM Classification: C.2.4: Distributed Systems