State dependency issues in evaluating distributed database availability

Quantitative evaluation of availability in distributed database systems must take into account both hardware and software failures. Therefore parameters such as the failure and the recovery probabilities must be evaluated for each “component” of the system.

The most difficult problems arise when the evaluation procedure has to deal with failure mechanisms which functionally depend on the state of the system.

In this paper, after a short introduction to a general methodology for availability evaluation, an example of state-dependent fault mechanism is described together with a technique for evaluating its impact on the life of the whole system.