Availability of continuous service and computing long-run mean time between failures and reliability for Markov systems

Steady-state availability has long been a popular descriptor of effectiveness for repairable systems because it captures both the operability and repairability aspects of the system. A related measure of effectiveness is the availability of continuous service, which is particularly relevant for safety critical applications. In this article, two different measures of this quantity are described for a repairable system whose state is described by an ergodic finite-state-space continuous-time Markov chain. Using these ideas, formulas for computing system long-run mean time between failures and the long-run system reliability function are derived.