Evaluation of Real-Time databases in a control-system setting

Abstract: This thesis is related to the knowledge area of real-time systems and real-time databases. The increasing complexity of the systems, specifically the embedded systems, and the need of store and share the information they use leads to the need of new technologies. For this reason a need of real-time database management system has emerged to satisfy the new requirements. Several commercial database systems claim to be real-time, but this technology is not consolidated enough. The thesis will perform an evaluation of those databases mainly in predictability terms since predictability is necessary for the correct execution of hard real-time systems. In order to complete the evaluation, a real-time database application has been implemented. This application implements two commercial databases, namely Mimer and eXtremeDB, and a monitor application which is responsible for displaying all the relevant database behavior’s information at runtime. A comparative studying of both databases has been carried out in order to determine how predictable these databases are. Parameters such as response time, CPU time consumption, etc has been studied. Finally, it can be concluded that both databases are predictable to a certain level. On one hand Mimer has an estimation of the worst case response time around 12 µs and CPU overload of 36%, and the fluctuation along the transactions is nearly negligible. On the other hand, eXtreme has an estimation of the worst-case response time around 18 µs and CPU overload of 41%, and the fluctuation along the transactions are rather bigger than the Mimer’s. However, it can be concluded that both databases provide real-time transactions and, thus, they are able to be implemented in real-time systems.