“…In other words, when the server leaves the system, it generates a sequence of vacation (or maintenance) segments each of which ends up with the server returning to the system and checking on its status. The whole vacation period is suspended (until its next occurrence, when the queue is exhausted or, in a quorum option [4,9,10,13], drops below some specific level) whenever the system accumulates to some fixed number of units or more and this prompts the server to resume his work [1,4,9,10,11,18]. When using semiregenerative analysis it is imperative to know the status of the system on the period prior to the completion of the first service.…”