Once the Critical Chain (CC) is identified, it becomes the baseline to measure project progress. A stable CC is therefore a requirement.
The Critical Chain is only recalculated or revised if there is very significant new work added to the project.Then progress must be measured to the new CC.
CCPM compares the percentage of Project Buffer consumed to the percentage of the Critical Chain that has been completed. (This is based on the time used versus the work completed.) This ratio is a direct indicator of the project health. If the buffer is consumed faster than the critical chain is being worked, management attention may be needed.