Critical chain primer

Using CCPM to reduce
lead-time in multi-project
environment…
…by automating and enforcing global
priorities through buffer management
Dan Klarman 20.2.2014

All Rights Reserved © Dan Klarman // Simple DO 2014

Agenda
• We will discuss the more technical aspects of CCPM
• We will discuss „only child‟ estimates.
• We will cover the different buffers that are used to
prevent interference between tasks and interference
between projects.
• We will explain how to use them:
1. Reliable Pipelining.
2. Focus Management attention at the right time at the right
place.
3. Allow self-organization of task sequence according to
dynamic global priorities.

Major Elements of CCPM
Fever
Chart

B
A
C
D

B

Single
Priority
System

E

Buffering
&
Pipelining

Major Benefits of CCPM
• Shorter Lead Times – 25%-50% reduction + DDP > 90%
• Optimal utilization of scarcest resources
• Focused Management attention & action at the right
time, at the right place
• Synchronized efforts through self-organization around
global priorities
• Eliminates Multitasking and allows focus and flow –
higher productivity and quality
• No more fire-fighting!

Definition of Critical Chain
Critical Path:
•
•

Critical Chain:

The longest chain of logically
dependent activities on the
project grid.
Defines the shortest possible
time to complete the project?

•

Critical Path

+
•

Finite Resources


Aggressive-But-Possible Estimates
„Only-Child‟ Estimates

Hidden Safeties

• Allows resource contention
to be addressed in planning
(instead of execution)
• Exposes real potential of
the system and real benefit
of adding resources
• Protects against:
–
–
–
–

Multi-Tasking / Interrupts
Parkinson's Law
Student‟s Syndrome
Programmer‟s Syndrome

Probability of finishing within time ‘t’
Median (50%)

T

Mean (80%)

T


4 Kinds of Buffers
• Project Buffer:
Aggregates Safeties on the Critical Chain.
• Feeding Buffer:
Protects the critical chains from disturbances on other chains.
• Resource Buffer:
Makes sure that the critical resource is never starved or
blocked.
AND
Protects projects from each other.
• Protective Capacity:
It is a virtual buffer that allows the critical resource to recover
in case of delays.

1st Kind of Buffer
Project Buffer

Remember: Safeties

• Aggregates Safeties from
individual tasks on the CC
into one buffer.
• Protects against:

Probability of finishing within time ‘t’
Median (50%)

Mean (80%)

– Uncertainty in task
execution.
– Planning Errors.

• Size: 50% of all safeties
on CC
T

T


How to create the Project Buffer
Actual Work

Safety

We cut out all thee safeties of the individual tasks and
aggregate half of them at the end of the project,

-25% LT
This way we are protecting the project deadline and not
the individual tasks…


Buffer Consumption in Execution


2nd Kind of Buffer
Feeding Buffer
• Aggregates Safeties from
individual tasks on NCCs
into one buffer.
• Protects the critical chain
from disturbances on
other Chains.
• Size: 50% of safeties on
the feeding chain.

When FB is consumed…
Then the CC „jumps‟…
and further delays are
then consumed from the
Project Buffer.
Proper Buffering ensures
that this rarely happens.


How to create the Feeding Buffer


3rd Kind of Buffer
Pipelining the CCR

The Resource Buffer

Although there can be more
than one scarce type of
resources there can only be
one scarcest resource.
This CCR is the „drum‟:
dictates the overall throughput
of the organization.
Good planning takes
scheduling the drum Seriously!

Makes sure that the drum is
never starved and enjoy early
finishes.
Protects projects from delays in
other projects.
Prevent delays from breaking
down the entire schedule of the
drum – no re-planning is
necessary.
Size: 50% of up-stream safeties
on CC (subtracted from the PB)


Pipelining Projects into the CCR
What Happens if this task is late?

What Happens if this task finishes early?

100%
CCR Load
Planning

Free
Slot

Free Slot
Free Slots
Future

Now


Inserting the Resource Buffer


Inserting the Resource Buffer
A chunk of the Project Buffer is moved in front of
the CCR tasks (Deadline stays the same)

Delays are now not passed on between projects any more – the
planning is stable

If the drum is released early from a project, the next
project is ready to take it!
100%
Load
Planning:
Future
Now


The Virtual Buffer (4th Kind)
Protective Capacity

Queuing Theory:

Even when well-buffered, there
is still the issue of how to deal
with variations of the drum itself.
By putting a planned load of no
more than 80% on the drum, we
allow it to „catch up‟ in case it is
needed – without exhausting it.
Otherwise the planning is always
over-optimistic and delays
cumulate quickly until planning
breaks down into chaos.

Effect of bottleneck load
Lead-time

Productivity

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Load on Critically Constrained Resource


Keeping Protective Capacity

100%
Load
Planning:

Protective Capacity

80%

Future
Now


Using The Buffers
…to focus management attention to the right place
at the right time!

Using the buffers: Teams
Global Priority:
•
•
•

Integrated Task List:

The color of tasks is dictated by the
status of the buffer at the end of the
chain.
Resource Managers assign and
execute tasks according to the global
priority.
3 Rules:
1.
2.
3.

Tasks on the CC are always done
before non-CC tasks
Within each group tasks are
executed by color
A new task is assigned to the first
available resource (after finishing
their previous task)

Proj.

Task

Est

Elps

W2C Asgn

B

#23

3

5

7

A

#42

3

2

1 Yuval

C

#03

5

-

-

-

C

#10

10

3

5

Dvir

A

#35

5

1

3

Tami

Dan

C

#04

3

-

-

-

D

#01

20

3

30

Itai


CC
Tasks

Non-CC
Tasks

Using the buffers: PMs
Fever Chart PM Dashboard:
100%
Ignore

Work Completed

Focusing in the right place
• Project Managers Track
the consumption of all
three types of buffers in
their project and plan
ahead accordingly.
• For example, by securing
more resources.
• If needed, they can
escalate.

Watch

75%

Plan
Act

50%

Late!
PB

25%

FB
FB2

0%
0%

33%

67%

Buffer Consumed


100%

Using the buffers: MGMT
Focusing in the right place

Fever Chart MGMT Dashboard:
Ignore

100%

Work Completed

• Managers need only to
look at the fever chart
in order to know where
to focus their attention.
• For each project, the
sum of PB + RB is
shown.

Watch

Plan

Act

Late!

B

75%

C

A

50%

D
B

25%

E

0%
0%

33%

67%

Buffer Consumed


100%

Variations
This one shows how both Uncertainty
and Flexibility reduce over time

• Regions can be chosen
differently so that
projects are compared on
the same scale.
• Axes can be switched so
that focus is on task
completion and not buffer
consumption.
• The goal is to drive the
right behavior…

Ignore

100%

Lead Time Remaining

There are variations…

Watch

Plan

Act

Late!

F
75%

E

50%

D

C

25%

B
A

0%
0%

Work Completed

All Rights Reserved © Dan Klarman // Simple DO 2014s

100%

More 1
• In some organizations a black task (already late) triggers
a stop-and-switch flag.

• What about ASAP projects / Red Carpets?
Even ASAP projects usually interface with other
activities through deadline…
SO…
• …The easiest way to ensure their priority is to cut the
due-date such that their buffer is Red or Black to begin
with.
This can also be done on the fly by planners.

More 2
• POOGI:
The size of the buffers can be adjusted over time
such that the majority of projects finish as
Yellow, and never Black.
• Buffer Analysis:
It is possible to analyze Red and Black transitions to
identify areas where local improvement process is
needed.

Q&A
Thank You!


Common Symptoms
Extra Material


What does “Global Priority” Means? (1)
Often, the involvement of a specific resource is needed in more
than one project simultaneously.
Often, there are no clear-cut answers available to the resource
manager, regarding the following questions:
– Which project should I work on first?
– In which cases should I stop what I am doing now and immediately
switch to work on something urgent?
– Should I focus my efforts and work serially to make sure each work is
finished at the shortest possible time?
– Or, should I work in parallel to reach maximum utilization of resources
I am responsible for?
– When is the right time to spend time on maintenance / training /
vacations, etc.?

The result is that each resource manager chooses their own answers. This leads to an
overall waste of precious resources through several mechanism.
•

Unnecessary Multitasking:
–
–
–
–

•

Setup times
Context Switching
Preventable errors and resulting rework
Lack of „flow‟ state

Unsynchronized Resources:
–
–
–
–

–

Unnecessary early start: hurts responsiveness to changes
Confused communication and interrupts: takes longer to get answers
War-fog: need to keep track of information about too many things
Longer lead-times: results in more “live” projects contending for same resources at the
same time
Starvation of Critically Constrained Resources (bottleneck): directly impacts throughput!


When efforts are not synchronized, and a fog-of-war is
created, management tends to over-react to noise in
the system and under-react to real risks.
This fire-fighting mode reflects in management overriding local priorities (which is good), but the new
priorities tend to be unstable – which is VERY bad…
…because it enhances the waste factors mentioned
before!

Over time, a Vicious-Cycle is created:
• During planning:
– Everybody starts to “Sand-Bag” their estimates to account for interrupts
and multitasking.
– Distrust regarding estimates and priorities leads to “Silo-Thinking”.

•

During execution:
– Longer and longer projects means more projects are running at the same
time with more resource contention. This make the system even more
erratic, which leads to more interrupts and more Sand-Bagging…
– Plans derail very quickly and updating them becomes impossible, and preemptive risk management becomes imaginary.
– Constant fire-fighting leads to neglect of maintenance and HR activity
which has negative long term effects on the organization.
– Finally, there is too much noise to think strategically…

What can we do?
Step 1: Place CCPM buffers in staggered
project plans
•

•

•

•

•

•

1st Pass: Starting with the WBS, and working
backwards (finish-to-start) we build a late-start
PERT, using „single-child‟ estimates.
2nd Pass: Stagger ANY resource contention on
specific atomic resource unit. Make all activities on
the CCR as contagious as possible (or move CCR).
Critical Chain: Identify the longest chain of
dependent activities (logic / resources) as the
Critical Chain.
Resource Buffers: Place a RB of 50% of up-stream
critical chain before the CCR (to make sure it is
never starved).
Project Buffer: Place a PB of 50% of down-stream
critical chain (from the CCR) at the end of the chain.
Feeding buffers: Place 50% FB at the end of chains
feeding into the critical chain.

Step 2: Pipeline projects to stagger load
on CCR
•

•
•

Pipeline: On a single GANTT, stagger all projects
according to load on the CCR (bottleneck), don‟t
load it over 80%!
3rd Pass: Stagger non-CCR contention if
present, add non-CCR resources if needed.
4th Pass: Stagger release dates of projects to allow
management to focus on kicking-off one project at
a time.


How far down the cycle is your
organization?

Critical chain primer

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