Commit Protocols in Mobile Environments: Design & Implementation

Abstract

In any database environment either wired or wireless, if multiple host access similar data items it may lead to concurrent access anomalies. As disconnections and mobility are the common characteristics in mobile environment, preserving consistency in presence of concurrent access is a challenging issue. Most of the approaches use locking mechanisms to achieve concurrency control. This leads to increase in blocking and abort rate in mobile environments. However the dynamic timer adjustment strategies may use locking mechanism to efficiently implement concurrency control. To reduce deadlocks and blocking of resources an enhanced optimistic approach for concurrency control is proposed. To show the effectiveness of the commit protocols in mobile environments, a simulator is designed and implemented to demonstrate how the transactions are committed and how the data consistency is maintained when the transactions are executed concurrently. The simulator was tested for both pessimistic and optimistic approaches.

Lock-free hybrid concurrency control strategy for mobile environment

“…The following simplifying assumptions have been used throughout this research and have been widely adopted in the literature [2,3,8,10].…”

“…Several works [1,3,[4][5][6][7][8] implemented the concurrency control strategies in mobile environment but because of the complexities of the issues to be considered such as mobility, low-bandwidth, frequent disconnection, low battery etc., most of the approaches were characterized by problems like deadlock, starvation, time lag between local and global commit, higher rate of abort, unnecessary restart.…”

“…It is one of the important components of transaction management, where its main requirement is to ensure correctness of shared data item when updated by multiple transactions at the same time [1,2]. In order to preserve data consistency, concurrency control is used in Database Management Systems (DBMS) so as to ensure transactions isolation whenever there are concurrent operations requesting access to the same object; which must be coordinated in order to prevent inconsistencies [3].…”