SWIFT: A Distributed Real Time Commit Protocol

IntroductIon Many applications such as military tracking, medical monitoring, stock arbitrage system, network management, aircraft control, factory automation, and so forth that depend heavily on database technology for the proper storage and retrieval of data located at different remote sites have certain timing constraints associated with them. Such applications introduce the need for distributed real-time database systems (DRTDBS) [Ramamritham, 1993]. The implementation of DRTDBS is difficult due to the conflicting requirements of maintaining data consistency and meeting distributed transaction's deadlines. The difficulty comes from the unpredictability of the transactions' response times [Huang, 1991]. Due to the distributed nature of the transactions and in presence of other sources of unpredictability such as data access conflicts, uneven distribution of transactions over the sites, variable local CPU scheduling time, communication delay, failure of coordinator and cohort's sites, and so forth, it is not easy to meet the deadline of all transactions in DRTDBS [Kao & Garcia – Monila, 1995]. The unpredictability in the commitment phase makes it more serious because the blocking time of the waiting cohorts due to execute-commit conflict may become longer. Hence, due to unique characteristics of the committing transactions and un-predictability in the commitment process, design of an efficient commit protocol is an important issue that affects the performance of DRTDBS [Shanker, Misra & Sarje, 2006d].