Abstract Distributed Real-Time DBMS (DRTDBMS) is a collection of Real-Time DataBase Management Systems (RTDBMS) running on sites connected together via communication's networks for transaction processing. This system is characterized by the data distribution and the unpredictable transactions. In addition, in this system, the presence of several sites raises the problem of the unbalanced load between those nodes. In order to enhance the performance of DRTDBMS with taking into account those problems, Quality of Service (QoS) based approaches are the most appropriate. Distributed Feedback Scheduling Control Architecture (DFCSA) is proposed for managing the QoS in this system. In DRTDBMS, the results produced in time with less precision are sometimes preferable than exact results obtained in delay, inaccuracy can be tolerated. In order to take this assertion, in this paper, we extend the DFCSA by using the (m, k)-firm constraints, which take into account the imprecise results, using three data replication policies. The obtained architecture is called (m, k)-firm-User- DFCS. The second contribution consists of taking into account the real-time derived data on (m, k)-firm-User-DFCS architecture, always, using three data replication policies. The obtained architecture is called Derived Data Management (DDM)-(m, k)-firm-User-DFCS. Then, we are focusing on two ways of service optimization in DRTDBMS. We are interested in (1) the space optimization in which we propose to apply three replication data policies, and (2) the QoS optimization in which we propose to take into account the real-time derived data and (m, k)-firm constraints.

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[18] Wei Y., Son S., Stankovic J., and Kang K., “QoS Management in Replicated Real Time Databases,” in Proceedings of 24th IEEE International Real-Time Systems Symposium. IEEE Computer Society, Cancun, pp. 86-97, 2003. Malek Ben Salem obtained his Bachelor’s degree in Computer Science from Sfax University. Then, he obtained his Master’s degree in Real-Time Computing Science from Sousse University and pursuing Ph.D in Computer Science in Sfax University. Currently, he is a Principal Professor at Monastir University. His current research interests are quality of service, distributed computing and real-time systems. Emna Bouazizi is an Assistant Professor at the University of Monastir, Tunisia since 2012. She has defended her PhD in April 2009 on Quality of Service Management in Real-Time Databases. Her main topics of research are Real-Time Databases, Ontology specification, Geographic Information Systems and Data Warehouse. Claude Duvallet is an Associate Professor in Computer Science at Le Havre Normandy University. He received his PhD in 2001. He is a member of the Intelligent Transport Systems team in the laboratory LITIS. His current research interests include real-time database systems, wireless sensor networks, vehicular ad hoc network and distributed multimedia system. He is also working on port logistics and marine traffic. He participates at many research projects on the topics of intelligent transport systems. Rafik Bouaziz is Professor Emeritus on computer science at the Faculty of Economic Sciences and Management of Sfax University, Tunisia. He was the president of this University during August 2014 – December 2017, and the director of its doctoral school of economy, management and computer science during December 2011 – July 2014. His PhD has dealt with temporal data management and historical record of data in Information Systems. The subject of his accreditation to supervise research was “A contribution for the control of versioning of data and schema in advanced information systems”. Currently, his main research topics of interest are temporal databases, real-time databases, information systems engineering, ontologies, data warehousing and workflows. Between 1979 and 1986, he was a consulting Engineer in the organization and computer science and a head of the department of computer science at CEGOS-TUNISIA.