The impact of prolonged service time under off-service placement on flexibility configurations

Abstract

In service systems, resource pooling is often introduced to cope with the variability in customer demand given a fixed service capacity for each service provider. The initial motivation for a more flexible system is to use the resources efficiently, that is, assign customers whose dedicated resources are fully occupied to available non-dedicated resources (referred to as off-service placement). In such a setting, the service system manager expects more customers to be served during a fixed period. However, recent empirical observations find that the service time at the non-dedicated service provider is significantly prolonged compared with that at the dedicated service provider. This study models these empirical observations by developing stochastic models to assess the impact of the prolonged service time and other parameters (system workload and asymmetry level) on flexibility configurations. We show that partial flexibility may outperform full flexibility in an asymmetric system with prolonged service time. Meanwhile, in the existing literature, the well-believed message is that a limited amount of flexibility, if adequately configured into the system, can achieve most benefits of full flexibility instead of surpassing it. In particular, we obtain conditions characterizing the optimal flexibility design in the parameter space. These conditions enable service system managers to make better flexibility designs when service time could be prolonged under off-service placement.

Keywords: Off-service placement, prolonged service time, flexibility designs, queueing models