Newsletter Article - Critical Chain Project Management

May 5, 2016
Team SQC, Uncategorized

Software Quality Center LLC is a reputed partner of the CMMI Institute.  We have been using CMMI® to help elevate performance for over 15 years and have seen the value of the models to deliver measurable results for our Clients/Organizations. We look forward to continuing to work alongside the CMMI Institute to extend the reach of the CMMI® frameworks to enable individuals and organizations to reach their goals.

We are pleased to share articles written by our Consultants, few of them with you, over the course of next few months, which you will enjoy reading and enjoy as a take-away for your everyday meetings and knowledge. It is also a great way to reinforce concepts of quality in your organization's staff in everyday meetings!  


Critical Chain Project Management

This article covers the solution provided by Dr. Eliyahu M Goldratt towards projects which follow the PERT/CPM method of project planning and execution.

Current Project Management Study

In projects today the end date is the one that needs to be protected most, so relating to this if we consider the plan, then the "Critical Path" is the one which needs to be protected the most. Why? Because the critical path is the one that decides the end date, and any delays to the critical path will lead to delay in the end date. Which means we need to know precisely when each task on the critical path is completed- a commitment. Since each tasks end date is to be treated as a commitment, the estimators tend to add buffers (Safety) at the task level to ensure that they can be 90% confident of meeting the task committed date. There are a few unintended consequences to the safety being added to each task

  1. Student's syndrome: Knowing that there is already a safety built in, the members will start the task late, and slowly eat up the buffer
  2. Parkinson's rule: Work will extend to the time provided, as the focus is to complete the task "ON" time.

This leads to the buffers being wiped out and if there are any issues at a particular task on the critical path, the end date gets impacted.

Other unintended consequences are if any member finishes early, they either do not report it or the subsequent task member is not ready to pick it up, so we lose out on any benefits to early finishes. Also, if the resources are responsible for multiple tasks both on the critical path and on the parallel paths, tend to multitask leading to further delays of the tasks.


The solution - Critical Chain Project Management

Based on these analysis, Goldratt built a complete solution and coined "Critical chain" as the longest chain of dependent steps and resources. The solution is based on 3 types of buffers introduced into the schedule and creation of a chain of activities considering tasks and resources.

Project Buffer: The first step is to take each task estimate and divide it by half, as by statistics, 50% confidence level is at half of the 90% confidence level. We move the 50% of the estimated effort to the end, and call it "Project buffer"

Feeding Buffer: This is to ensure that the non-critical path tasks do not create any constraints for the critical path. The activities on the critical path need to be able to start without waiting for any subcritical activities. So "feeding" buffers are added at the end of the non-critical sub paths.

Resource Buffer: Resource buffer is more of a communication being sent out like a beacon to all the appropriate resources who are to start off on the next task. This is to ensure that all the resources are prepared and ready for the tasks as soon as their turns comes in.

Creating the Critical Chain: When we are creating a critical chain, create the critical path first, and then rearrange the tasks and the resources such that there are no overlaps i.e., no multiplexing /multitasking for resources which are involved in multiple tasks.

Controlling the project: The project is managed by watching the Project buffer which is divided into three zones, the Green zone, Yellow zone and the Red zone. If the buffer is eaten upto the Red zone, then Project Manager will raise alarms and alert the customer of an impending delay, and start off with the corrective actions, pulling in more resources where necessary.

Please refer to Critical Chain Project Management by Eliyahu Goldratt and Theory of Constraints Handbook by James F. Cox III and John G. Schleier Jr.


Ravi Raghavendra (Sr. Consultant -SQC): He has worked in MNC companies in the area of Process improvement frameworks like CMMI for development and services. Established Software Quality improvements by leading teams to successfully achieve CMMI L5 and CMM L3 in multiple organizations. He has experience in Business improvement frameworks like EFQM, Establishing Product Realization Process, Architecting Business Process Improvements, Software development methodologies like V model, Agile (SCRUM) and Critical Chain Project Management.  


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