The Critical Chain Book Report

The Critical Chain Book Report

A critical path is the sequence of project network steps with the longest overall duration, determining the shortest time to complete the project. The duration of the critical path determines the duration of the entire project. Any delay of an important step on the critical path directly impacts the planned project completion date. For example, there is no slack on the critical path. A project can have several parallel critical paths. "Critical path is defined as the longest chain of dependent steps. Longest in time, of course" (Critical Chain; Goldratt).

The critical chain idea means that the weakest link is the project's constraint. Constraints can never really be eliminated. They simply move from one part of the system to another. In project management, the critical chain is the sequence of both precedence and dependent terminal steps that prevents a project from being completed in a shorter time. If a resource is not a constraint, then a project's critical chain is identical to its critical path. The critical chain "removes resource contention within a project. It does not address resource contention between projects at all" (Critical Chain; Goldratt).

As critical path considers that dependencies between steps can be a result of a path or a result of a common resource. So, the longest chain will be composed of sections that are path dependent and sections that are resource dependent. Unlike the critical path method, the critical chain method eliminates safeties from each task. It doesn't look for a task starting and finishing "on time." The critical chain method will theoretically start the right step, at the right time, using a list of priorities. Unlike the critical path method, it also focuses on meeting milestone dates, not task dates. Also, the critical chain focuses on "task throughput, not task costs."

Inventory buffers are analogous to "the length of the ropes" in project management. Buffers offer protection against delays and create more flexibility as you fit changes into your schedule. The kinds of buffers used to manage projects include project, feeding, and resource buffers. The Project Buffer protects the promised due date from variation in the critical chain. A project buffer is inserted at the end of the project network between the last task and the completion date. Any delays on the longest chain of critical tasks will take some of the buffer, but will leave the completion date unchanged. The feeding buffer protects the critical path from delays occurring in the analogous noncritical paths. When the problem causes a delay bigger than the feeding buffer, the project completion date is still protected by the project buffer. Feeding buffers are inserted between the last task on a feeding path and the critical chain. Resource buffers can be set