An optimistic based algorithm for concurrency control in distributed databases

In this thesis an algorithm is proposed forconcurrency control in distributed databases . The algorithmuses the optimistic technique for r-w synchronization ,Thomas write rule (TWR) for w-w synchronization and thelocking to minimize the no of restarts.The proposed algorithm combines these techniques insuch a way to have the advantages of each one , namely theexcellent performance of the optimistic technique in lowarrival rate and read oriented environment , the advantagesof TWR in w-w synchronization and the small no of restartscaused by locking technique.Two interfaces are built to interface optimistictechnique with TWR and locking techniques. The interfacesintroduce one additional set called validate set and twoextra tables Read lock table and Write lock table to theoriginal optimistic technique. The validate set is used toovercome the effect of the proposed move of the transactionnumber from the end of write phase to the end of thevalidation phase. The two locking tables are used to lockthe database elements read or written by transactionrestarted two times.The algorithm is presented in details , the correctness