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Topics: New Practitioners, Schedule Management, Scheduling
Top differences between Critical Path & Critical Chain?

I've done lots of research on critical path, but I have little knowledge on critical chain.

Why was it created? What does it aim to achieve? What type of buffers and how are they different? How are buffers applied and why?

If someone could give me the top 5 differences between CP & CC I'd greatly appreciate it.
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I was fortunate to have been mentored by Eli Goldratt in TOC and Critical Chain. Goldratt shared the Critical Chain knowledge in his book, 'Critical Chain' in May 1997 and I implemented Critical Chain in a complex multi-project company in July 1997. CP is the longest chain of task dependencies whereas CCPM is the longest chain considering task and resource dependencies. This means that the Critical Chain (CC) may consist of predecessor / dependencies task and/or resource dependencies. This means there may be a physical dependency so a task may have to finish before you can stay the successor task (task dependency). If there is a resource dependency this means a task with a limited resource has to finish on the predecessor task and be available for the next task (there is no physical dependency). This is important in understanding the difference between CPM and CCPM - So a CC is not just a CPM with no resource contention a CCPM schedules both task and resources.

Sorry for just addressing just one difference but this is a basic building block in understanding CCPM - If there is interest I will gladly share additional differences and more importantly advantages of using CCPM

Knowingly or unknowingly we used CC in our projects. In real time every one will add buffer to project plan . How and where this can be added is what CC teaches.

Critical PAth is a good way to secure your project by having only one big buffer for your project.
It deals with some well knows syndroms in Prject management like student syndrom or parkinson syndrom.
The interesting thing is taht the buffer is mutualised and it good be followed precosely and some warnings could be putted in place to prevent a sidetrack on your project.

Jan 08, 2018 8:26 PM
Replying to Vincent Guerard
I invite you to go and complement the wiki on CCPM, you seem a good candidate to improve on the actual text.
Vincent, thanks for your suggestion. Took me a while to get back here, but I think I've improved Critical Chain. Will get to the others shortly. Thanks for the encouragement.

Aug 21, 2017 3:47 PM
Replying to Suhail Iqbal
To understand Critical Chain you must have some idea of Theory of Constraints. The crux of the matter is "A chain is as strong as its weakest link". What is the weakest link in project management plan. You cannot take any chances with critical path because any delay on CP is delay in project. Now the question is how to protect the critical path? We have to understand it as the weakest link and to protect it we need to establish buffers to ensure no project gets delayed due to the delay on critical path. If we add a buffer to the critical path in addition to the project duration, that is an increase in original duration which is not acceptable. We have to create this project from within the critical path without adding anything from outside. If we can tax the critical activities and borrow some time from each critical activity, we can put this accumulated time as buffer and restrain the critical activities to their new reduced duration. This project buffer is not in control of those activities from whom it was borrowed and it is the discretion of project manager now if he wants to allow some additional time to one of these activities in trouble, but as a whole a major portion of buffer is secure and is responsible for providing security to the weakest link, our critical path. This will ensure our project will never be delayed and therefore the chain is now string enough. This is called the critical chain.
Excellent explanation. Is the buffer taken from critical path also a source for building project buffer, at the overall project buffer ?

Critical chain project management (CCPM) is a method for planning and managing projects like Critical Path Method. It is different from CPM and PERT because it relies on resource levelling and resource availability rather than activity sequences. 


my thesis topic is "the performance evaluation of buffer sizing methods in CCPM and develop an comprehensive model to buffer sizing in CCPM"
there are more than 32 methods for buffer sizing in CCPM from 1997 until 2018!!!
the most important matter which is not pay attention, is Fever Chart and the Action Rate Index in planning phase.
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