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).