(m,k)-firm model has recently drawn a lot of attention. It provides a flexible real-time system with graceful degradation of the QoS, thus achieving the fault tolerance in case of system overload. In this paper we focus on DBP algorithm as it presents the interesting feature of dynamically assigning the priorities according to the system's current state (QoS-aware scheduling). However, DBP cannot readily be used for systems requiring deterministic (m,k)-firm guarantee since the schedulability analysis was not done in the original proposition. In this paper a sufficient schedulability condition is given to deterministically guarantee a set of periodic or sporadic activities (jobs) sharing a common non-preemptive server. This condition is applied to two case studies showing its practical usefulness for both bandwidth dimensioning of the communication system providing graceful degradation of QoS and the task scheduling in an in-vehicle embedded system allowing fault tolerance.