Performance comparison of concurrency control protocols for transaction processing systems with regional locality

Abstract

An examination is made of a system structure and protocols to improve the performance and availability of a distributed transaction processing (TP) system when there is some regional locality of data reference. Several TP applications, such as reservation systems, insurance, and banking, belong to this category. While maintaining a distributed system at each region, a central system is introduced with a replication of all databases at the distributed sites. It can provide the advantages of distributed systems for transactions that refer principally to local data and of centralized systems for transactions accessing nonlocal data, and it can provide better availability. Specialized protocols can be designed to keep the copies at the distributed and centralized systems consistent without incurring the overhead and delay of generalized protocols for fully replicated databases. The authors study the advantages of this system structure and the tradeoffs between protocols for concurrency and coherency control of the duplicate copies of the databases. An approximate analytic model is used to estimate the system performance, and the method is validated through simulations. The performance is confirmed to be sensitive to the protocol, and substantial performance improvement over general distributed systems can be obtained.