A Comparative Study on Replenishment Policies for Perishable Inventory System with Service Facility and Multiple Server Vacation

In the continuous review inventory systems the most widely used ordering policy is (s, S) policy, also known as Two-Bin policy. In the case when the stocked items can perish, fail, or become useless after a random time, this policy may not be optimal, as after placement of an order more items may perish with less number of demands during the lead time. If we allow vacation of server when no-customer or no-item in the system, the replenished stock at the end of vacation, may be lower than the reorder level, viz., s. This calls for the placement of additional order and we propose to place order (1) of fixed size, (2) that replenishes the stock to full capacity, or (3) of variable size depending on the level at the time of ordering. An attempt has been made in this paper to make a comparative study of these policies under a broad set-up consisting of MAP arrivals for both regular customers and for negative customers, random life time for items, single server, infinite waiting hall, multiple (one-after-another) vacations of random length, random service time and random lead time. After deriving the necessary equations (in steady state) for various measures of system performance, an extensive numerical study is provided.