  Performance of object-oriented database systems (OODBs) is still an issue to
both designers and users nowadays. The aim of this paper is to propose a
generic discrete-event random simulation model, called VOODB, in order to
evaluate the performances of OODBs in general, and the performances of
optimization methods like clustering in particular. Such optimization methods
undoubtedly improve the performances of OODBs. Yet, they also always induce
some kind of overhead for the system. Therefore, it is important to evaluate
their exact impact on the overall performances. VOODB has been designed as a
generic discrete-event random simulation model by putting to use a modelling
approach, and has been validated by simulating the behavior of the O2 OODB and
the Texas persistent object store. Since our final objective is to compare
object clustering algorithms, some experiments have also been conducted on the
DSTC clustering technique, which is implemented in Texas. To validate VOODB,
performance results obtained by simulation for a given experiment have been
compared to the results obtained by benchmarking the real systems in the same
conditions. Benchmarking and simulation performance evaluations have been
observed to be consistent, so it appears that simulation can be a reliable
approach to evaluate the performances of OODBs.
