In inventory control theory, suitable models for various real life systems are constructed with the objective of determining the optimal inventory level. A new type of inventory model using the so-called Setting the Clock Back to zero(SCBZ) property is analyzed in this paper. There are two Machines M1 and M2 in series and the output of M1 is the input for M2 and hence in order to avoid the machine M2 is being idle when the machine M1 is in breakdown state, a reserve inventory is to be maintained between M1 and M2. The method of obtaining reserve Sˆ , assume the cost of excess inventory, cost of shortage and rate of consumption of M2 is constant is already attempted. In this paper it is
assumed that the repair time of M1 is a random variable and its distribution undergoes a parametric change after the truncation point and which is taken to be a random variable. The optimum reserve inventory is obtained under the assumption that the repair time having the SCBZ property. Numerical illustration is also discussed.