Buffer Management

Within this article, we will explain the basics of CCPM behavior and how to include buffers into your plan. By using buffers, we can determine the priority of a specific project in comparison to the rest of the projects within the Project Portfolio. 

CCPM Priority for individual projects

CCPM priorities are determined by the amount of Buffer Consumption versus the amount of Progress, also called Longest chain complete versus the Original Critical Chain. Plotting this information in a progress or fever chart will provide you insight how your project compares to your total project portfolio.

A project may have, besides a project buffer and its feeding chain, also one or multiple milestone buffers, with each have their own milestone feeding chain. In the Lynx progress chart (Fever chart) the CCPM priorities for both type of chains (project and milestone) will be plotted. 

In LYNX each task and feeding chain is inheriting what is called the Most Critical Buffer:

• If a project only has a project buffer, it's by definition the most critical buffer.
• If a project has multiple buffers (milestone buffer(s) and/or a project buffer) the most critical buffer is the buffer with the highest CCPM priority.

Progress Chart - CCPM Priority for the Project Portfolio

In the "Portfolio" view below for both projects the buffer indexes are shown:

• Project A has achieved 20 % progress and has 60 % buffer consumption
• Project B has achieved 10 % progress with 60 % progress

In the example above Project A and Project B have both 60 % buffer consumption. However, the progress for both project is different. If we plot this on the Progress chart, we will have the following view:

This results in the fact that the distance to the demarcation line is the largest for Project B, because this project has less progress and therefore this project has a higher CCPM priority. Therefor, Project B will be put on top of the list, above Project A in the Project Portfolio. 

The CCPM Priority is determined by the position of the Buffer Index in the progress chart compared to the demarcation line between the "Red" zone and the "Orange" zone. 

Note: in the article the examples use the Traditional Feverchart Strategy. An alternative Feverchart Strategy is described in this article: Portfolio Feverchart Strategy Configuration.

Adding buffers into your plan

Now you know the basics for CCPM priority. If you want to read more about the background of this theory, please read Understanding (CCPM) Priority Behavior. We wil now explain how to use this within your project plans in Lynx. Therefor, we start with a short explanation about buffers.

Buffer types

There are three types of buffers that could be used within Lynx projects:

1. Project Buffers
   • There is only 1 project buffer at the end of a project.
2. Feeding Buffers
   • There can be multiple feeding chains, which can have their own feeding buffer
3. Milestone Buffers
   • A deadline defined for a task is considered to be a Milestone;
   • The chain leading to a task with a milestone will have a milestone buffer.
4. (Resource Buffers)
   • Extra: applied during the "stagering process"- not described within this document.

Adding buffers to your project

Example project

For this article, we have the following example project without buffers:

As you can see, task 4 (End Prototype) has a milestone at the 14th of September. You can add a milestone yourself by selecting the tab constraint within the bottom of your screen and fill in the Deadline date at the right side.

CCPM configurations

If you haven't released your project yet (Project Properties -> Status: Not Started). There will be three buttons in the top right behind the text CCPM. The button that can be found at the far right side is to open the CCPM Property dialog. Within this dialog box, you can select the bufferpercentage that you would like to add to the different buffers we described above: the Feeding, Milestone and Project buffer, see figure:

There are two ways to add the buffers into your project:

1. The Insert Buffers button at the screen that you just opened.
2. Directly via the CCPM button with the '+' sign 

Within this dialog, you find the same settings as within the CCPM Property Buffer Creation, but with an additional button: Create Buffers. Press the button and the buffers will be added to the project: Operation has completed.

Other CCPM Parameters

Besides the percentages of the buffer, there are more CCPM Parameters that you can configure here:

• Automatically detect and mark critical chain tasks
  • Automatically provides information about the tasks on the Critical Chain/ Current Longest Chain (red) and feeding tasks (blue)
• Automatically shorten task durations by (%)
• Buffer creation:
  • Consume feeding buffers when they extend the duration of the CC
  • Consume milestone buffers when they extend the duration of the CC
• Expected buffer consumption (%)
  • Basis for the buffer consumption using the debuffered view (standard: 100%)

If you want to have more information about these articles, please select the header and read the article that's attached.

Added buffers

After we have added the buffers (all percentages were 50%), we got the following result:

As you can be seen in the figure, a Milestone buffer is added on line 5 from 9 days, a Feeding buffer is added on line 7 from 2 days (only protecting task T6: Handover) and at the end of the project a Project buffer is added from 20 days, see figure:

This article is under development, for the original version see the PDF attached.