Scheduling a repairman in a finite source system

The scheduling of a single server in a finite source model is considered. The N customers in the system have different failure and repair rates. Also the costs depend on the customers which are broken down. The authors give a condition under which the average costs are minimized by a simple list policy, and with a counterexample they show that in the general case no optimal list policy may exist. This motivates us to derive policies which are optimal under low and high traffic condition. They are again list policies, which behave well numerically.