Conclusions

Abstract

Because of the increasing dynamics and uncertainties in the environment of companies, their planning systems must be able to react to unexpected developments. To cope with uncertainties, the planning system is usually embedded in a framework which permits the incorporation of new information into decision making from one planning period to the next, such as a rolling horizon schedule. The decisions at the top planning level provide input data for subsequent lower planning levels. Therefore, the adjustment of plans for a specific planning level may lead to additional uncertainties at adjoining planning levels. This may lead to a nervous planning system, in particular, since instability at the top level is propagated throughout the entire system. Since material coordination is the central element in the production planning framework, a “stable“ material requirements planning system is important to avoid the negative aspects of nervousness, like increasing costs through, e.g., increased overtime, or inventory. For material requirements planning systems, the problems resulting from frequent plan revisions have been discussed extensively in literature. Different strategies have been suggested for reducing nervousness, and the impact of a wide range of parameters of planning concepts and decision rules on instability has been examined. However, a systematic analytical investigation of nervousness for stochastic lot-sizing rules within a rolling horizon schedule has not yet been provided.