QoS Aware Replica Control Strategies for Distributed Real Time Database Management System

摘要

In distributed real time database management system (DRT-DBMS), QoS aware replication control strategy is necessary to ensure availability and to improve the system performance. Since user request and need of data is dynamic in nature, it requires an approach which addresses the problem of data distribution and also resolves them in DRT-DBMS. A large quantity of data file is produced so we need a dynamic replication approach through which we can reduce the data access time. In order to replicate it, at the nearest site, replica placement and replacement algorithms are required to be evaluated. This paper presents a heuristic approach Greedy-Cover Firefly algorithm in which replica is placed dynamically based on QoS requirement and replaced with the optimal adaptive replica replacement algorithm for each data object. The replication cost required for copying data object to each set of a node is calculated to select the optimal node. Here, the replication decision is taken on the basis of access history of data on multiple sites. Due to the limited storage capacity of each node, the value of each file is calculated, and the file with the smallest value is removed to replace other files. A detailed simulation shows that the proposed algorithms can greatly improve the system performance to reduce the system resources consumed with respect to time and QoS requirement.