Mobile agent based self-adaptive join for wide-area distributed query processing

In this article, optimization of decision support queries is considered in the context of wide-area distributed databases. An original approach based on the "mobile agent" paradigm is proposed and evaluated. Agents' autonomy and reactivity allow operators of the execution plan to adapt dynamically to estimation errors on relations and to evolutions in the state of the execution system, avoiding time overheads commonly associated with centralized monitoring. We present decentralized self-adaptive algorithms for dynamic optimization of join operators, and their implementations in Java using mobile agents. Then, we evaluate performance depending on error rate on statistical information on database, and on communication bandwidth and CPU frequency. The results show that the agent-based approach can lead to a significant reduction of response time and provide decision criteria for developing an effective migration policy.