A Concurrency Control Method Based on Commitment Ordering in Mobile Databases

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.Comment: 15 pages, 13 figures, Journal: International Journal of Database Management Systems (IJDMS

An Efficient Concurrency Control Technique for Mobile Database Environment

Day by day wireless networking technology and mobile computing devices are becoming more popular for their mobility as well as great functionality Now it is an extremely growing demand to process mobile transactions in mobile databases that allow mobile users to access and operate data anytime and anywhere irrespective of their physical positions Information is shared among multiple clients and can be modified by each client independently However for the assurance of timely access and correct results in concurrent mobile transactions concurrency control techniques CCT happen to be very difficult Due to the properties of Mobile databases e g inadequate bandwidth small processing capability unreliable communication mobility etc existing mobile database CCTs cannot employ effectively With the client-server model applying common classic pessimistic techniques 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 techniques aren t appropriate in mobile database as well This paper discusses the issues that need to be addressed when designing a CCT technique for Mobile databases analyses the existing scheme of CCT and justify their performance limitations A modified optimistic concurrency control scheme is proposed which is based on the number of data items cached amount of execution time and current load of the database server Experimental results show performance benefits such as increase in average response time and decrease in waiting time of the transaction

An Efficient Concurrency Control Technique for Mobile Database Environment

Day by day, wireless networking technology and mobile computing devices are becoming more popular for their mobility as well as great functionality. Now it is an extremely growing demand to process mobile transactions in mobile databases that allow mobile users to access and operate data anytime and anywhere, irrespective of their physical positions. Information is shared among multiple clients and can be modified by each client independently. However, for the assurance of timely access and correct results in concurrent mobile transactions, concurrency control techniques (CCT) happen to be very difficult. Due to the properties of Mobile databases e.g. inadequate bandwidth, small processing capability, unreliable communication, mobility etc. existing mobile database CCTs cannot employ effectively. With the client-server model, applying common classic pessimistic techniques 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 techniques aren`t appropriate in mobile database as well. This paper discusses the issues that need to be addressed when designing a CCT technique for Mobile databases, analyses the existing scheme of CCT and justify their performance limitations. A modified optimistic concurrency control scheme is proposed which is based on the number of data items cached, amount of execution time and current load of the database server. Experimental results show performance benefits, such as increase in average response time and decrease in waiting time of the transactions