A Concurrency Control Method Based on Commitment Ordering in Mobile Databases

TL;DR

This paper introduces the OPCOT concurrency control algorithm for mobile databases, which reduces transaction aborts and waiting times by combining optimistic control with commitment ordering, addressing disconnection challenges.

Contribution

The paper proposes the OPCOT algorithm, a novel concurrency control method that improves transaction management in mobile databases by reducing aborts and blocking.

Findings

OPCOT decreases transaction abort rates compared to 2PL and optimistic algorithms.

OPCOT reduces waiting times for transactions in mobile database simulations.

The serializability of OPCOT is proven using serializability graphs.

Abstract

Disconnection of mobile clients from server, in an unclear time and for an unknown duration, due to mobility of mobile clients, is the most important challenges for concurrency control in mobile database with client-server model. Applying pessimistic common classic methods of concurrency control (like 2pl) in mobile database leads to long duration blocking and increasing waiting time of transactions. Because of high rate of aborting transactions, optimistic methods aren`t appropriate in mobile database. In this article, OPCOT concurrency control algorithm is introduced based on optimistic concurrency control method. Reducing communications between mobile client and server, decreasing blocking rate and deadlock of transactions, and increasing concurrency degree are the most important motivation of using optimistic method as the basis method of OPCOT algorithm. To reduce abortion rate of transactions, in execution time of transactions` operators a timestamp is assigned to them. In other to checking commitment ordering property of scheduler, the assigned timestamp is used in server on time of commitment. In this article, serializability of OPCOT algorithm scheduler has been proved by using serializability graph. Results of evaluating simulation show that OPCOT algorithm decreases abortion rate and waiting time of transactions in compare to 2pl and optimistic algorithms.