Buffer Management

Buffer management is the key to managing a Critical Chain project. The Critical Chain methodology does not work without it. Project and resource managers examine buffer reports daily or weekly to determine what actions, if any, they must take. The time frame varies, according to the length of the projects. Buffer reports for short projects (e.g., less than one month) are examined more frequently. Senior management examines buffers weekly or monthly to determine if projects are in control or out of control.

Every task in a Critical Chain project is connected either to a project buffer or a feeding buffer. When a task takes longer than estimated, it eats into the buffer that it is connected to. Buffer penetration reports indicate when the project is in danger. They also indicate which current task is causing the problem.

The comparison of the percentage of the project buffer consumed to the percentage of the Critical Chain completed gives a partial picture. For example, if the project shows that 50 percent of the Critical Chain is completed, while only 20 percent of the project buffer has been consumed, the project is considered to be in excellent shape.

Looking at Figure 22-7, the first task is scheduled to take ten days. If the task takes fifteen days to complete, it has eaten five days from the project buffer. The status is then ten out of eighty-five days complete, or 12 percent. At the same time, we have eaten five out of the thirty-four days of buffer, or 15 percent. On the surface, this is close to normal. However, trends help the interpretation, as we will see below.

Since feeding buffers are shock absorbers on the noncritical paths, only after a feeding buffer is 100 percent consumed does the project buffer get impacted. Therefore, feeding buffers are watched, but are always a lower priority than a project buffer. For example, looking at Figure 22-7, the last task on the first path is to fabricate poles and bases, estimated to take ten days. This task will only begin to impact the Critical Chain after all four days of the feeding buffer are consumed.

The trend of buffer consumption compared to Critical Chain completion over time gives another key part of the picture. For example, consider the data in Figure 22-8.

Looking exclusively at one set of figures, for week 4, you observe that the project has eaten away 15 percent of the project buffer, while only 8 percent of the Critical Chain is complete. On the basis of this one set of figures, it looks like a crisis—something worthy of intervention. However, the trend shows exactly the opposite.

In week 1 of the project, 10 percent of the project buffer was consumed while only 2 percent of the Critical Chain was completed. One figure, by itself, should not alarm the project manager. However, it certainly is worth investigating.

By week 2, the project trend is rapidly deteriorating. We see that 20 percent of the project buffer is gone while only 3 percent of the project's critical chain is complete. This

Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

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