ИСТИНА

Queueing systems in which servers may be temporary unavailable for operation arise naturally as models of many computer, communication and manufacturing systems. Service interruptions may result from resource sharing, server breakdowns, priority assignment, vacations, some external events, and others. For instance, for queueing systems with preemptive priority discipline service interruptions for the low priority customers occur when a high priority customer arrives during a low priority customer's service time. Therefore, there is significant interest in the investigation of queueing systems with service interruptions. We consider a system with heterogeneous servers and a common queue. The input flow is assumed to be a regenerative one. The preemptive repeat different service discipline is investigated, i.e. service is repeated from the beginning with different independent service time after interruption. Sequence of availability cycles may consist of dependent elements, but it should have regeneration in some sense. By Q(t) denote the number of customers in the system. Let us formulate main results that hold under some not restrictive and natural conditions. Theorem 1 The process Q(t) is stochastically bounded if the traffic rate is less then one.