 What are buffers?
Buffers are allowances for common-cause variation in performance and uncertainty in estimates. They
aggregate the allowance for variation to a smaller total under
the control of the project manager.
What is the project buffer?
The Project Buffer is the buffer at the end of the Critical Chain. It determines the project completion
date, and is the tool used by management and resources to
make certain project decisions.
Size the Project Buffer based on the tasks in the feeding chain. The buffer size is the sum of a buffer
for bias plus a buffer for variation.
What are feeding buffers?
Feeding buffers are time buffers placed in project chains (paths) that tie in to the critical chain.
Their purpose is to help insure that the successor task on the critical
chain has all of its inputs with about a 50% probability.
Size the feeding buffers based on the tasks in the feeding chain. The buffer size is the sum of a buffer
for bias plus a buffer for variation.
What is the resource buffer?
The resource buffer is a flag to alert resources planned to work on the Critical Chain that their task
is coming up to be worked on. It is
necessary to prevent excessive queuing
for resources working on tasks on the
critical chain. Usually a prioritized
task by resource substitutes for this
funciton.
What is the capacity constraint buffer?
The capacity constraint buffer is a buffer used in the drum schedule to buffer the use of the drum resource
in one project to its use in the next project. The net result
of the capacity constraint buffer is to sequence the start of projects, rather than start them all at
once.
What is the drum buffer?
The drum buffer is only used in multi-project implementations. Its purpose is to exploit the early availability
of the drum resource by assuring all of the input tasks
are complete if the drum resource completes its task in the predecessor project early.
Rarely used.
What is the cost buffer?
The cost buffer is the necessary cost allowance to cover use of the project and feeding buffers. You
can size the cost buffer considering all of the tasks in the
project.
|