Conditional Availability of Intermittently-Used Systems in Non-Markov Environment

This paper discusses the steady-state conditional availability of intermittently-used systems during the periods of demand. All the distributions governing system and demand status are arbitrary. The history dependence of the system and demand behavior is tackled by introducing history and cumulative-history functions. The system is assumed to fail only in use. Two processing disciplines regarding an interrupted demand (due to a system failure) are treated: fail-resume and failrepeat. The steady-state conditional availability under the fail-resume discipline is MTBF/(MTBF + MTTR), but not under the fail-repeat discipline. Therefore, care must be exercised not to misuse the formula.