In this paper, we study discrete-time priority queueing systems fed by a la
rge number of arrival streams. We first provide bounds on the actual delay
asymptote in terms of the virtual delay asymptote. Then, under suitable ass
umptions on the arrival process to the queue, we show that these asymptotes
are the same. As an application of this result, we then consider a priorit
y queueing system with two queues. Using the earlier result, we derive an u
pper bound on the tail probability of the delay. Under certain assumptions
on the rate function of the arrival process, we show that the upper bound i
s tight. We then consider a system with Markovian arrivals and numerically
evaluate the delay tail probability and validate these results with simulat
ions.