This paper analyzes the effect of overbooking for scheduling systems in a commercial environment. In this scenario each job is associated with a release time and a finishing deadline as well as a fee for a successful execution and a penalty for violating the deadline. The core idea is to exploit overestimations of required job execution times, providing an opportunity to aggressively schedule additional jobs. The proposed probabilistic scheduler is based on histories of job execution times, device failure rates, and penalties for SLA service violations. This paper includes a theoretical background and a mathematical model of the overbooking approach and a simulative evaluation with a synthetic workload on a single-processor system.