Author:

Keywords:

Scheduling

Abstract:

The direct application of the Theory of Constraints (TOC) to project management, known as Critical Chain Scheduling and Buffer Management (CC/BM), has recently emerged as one of the most popular approaches to project management. It is the objective of this paper to highlight the merits and pitfalls of the approach. We offer a global overview of the fundamentals of CC/BM. The strengths and weaknesses of the CC/BM approach are put into perspective, based on a critical analysis of the literature as well as our own experimentation with commercial CC/BM software. The fundamental CC/BM principles and assumptions are tested in a full factorial experiment performed on a set of benchmark instances. Contradictory to CC/BM belief, regularly updating the baseline schedule and the critical chain at each decision point provides the best intermediate estimates of the final project duration and yields the smallest final project duration. Using clever project scheduling and rescheduling mechanisms such as branch-and-bound, has a beneficiary effect on the final makespan, the percentage deviation from the optimal final makespan obtainable if information would be perfect, and the work-in-process. Using the 50% rule for buffer sizing may lead to a serious overestimation of the project buffer size. The 2s-buffer size assumption does not hold. The beneficiary effect of computing buffer sizes using the root-square-error method increases with problem size. Keeping the critical chain activities in series is harmful to the final project makespan. The work-in-process impact of the scheduling mechanism used for scheduling the gating tasks is negligible. Recomputing the baseline schedule at each decision point is found to have a strong beneficiary impact on the final project duration.