The Quasi-Synchronous approach to Distributed Real-Time Databases

Carlos Almeida and Paulo VerĂ­ssimo

INESC Technical Report (RT/02-96)

Abstract

This paper addresses the problem of achieving predictable real-time behavior of distributed databases, over environments that do not exhibit hard real-time properties. Unlike soft real-time systems, our quasi-synchronous approach aims at achieving hard real-time properties, while given assumptions about the environment hold. As failures get more severe, applications pull back to successively more degraded operational envelopes, that still allow timing assumptions to hold. Timing failure detection and adaptive group communication protocols make this approach effective.

The approach is specially useful for telecommunication information network databases, which have to support emerging services that are ever demanding in terms of availability, performance and responsivity. We argue that a soft real-time approach does not deliver the quality of service expected of these databases. In this paper, we use this example application to illustrate how our approach and architecture can support these services effectively.

Also available as INESC RT/02-96 (gzip postscript).