Critical Chain

Copyright 2000 by ProChain Solutions, Inc.http:/ /www.prochain.com

Practical Critical Chain Scheduling

Primavera User ConferenceDecember, 2000

Rob NewboldProChain Solutions Inc.

(703) 490-8821 www.prochain.com


1. Introduction

BackgroundAgenda

Critical Chain Scheduling (Readers Digest) Practical Recommendations


Practical Methodology

When managing projects in a business context, methodology is how we do what we do to ensure high quality, repeatable results.1

The question isnt how we schedule projects, its how we solve business problems.

Practical business solutions must integrate tools, procedures and rules.

* The M-Word Explored, Tony Nish, PM Network, September 1999, p. 67.


2. Critical Chain Scheduling

Single Project SchedulingMultiple Project Scheduling


Step 1: Create the Project Network

5:Design 2:Dev

2:Dsn 3:Proto 4:Dev 2:Tst

Must be reasonableChallenge all assumptions, such as

resources, dependencies, durations Ideally, use average touch time for task

durations: no allowance for uncertainty


Estimating Task Times

3 wks

50%

6 wks

90+%

Add an allowance for uncertainty

10 wks Add an allowance for other projects

These are the estimates that usually go into our project schedules


5:Design

2:Tst

Step 2: Identify The Critical Chain

B.) Then identify the Critical Chain

The Critical ChainThe longest path through the network considering

both task and resource dependencies

A.) First, eliminate resource contention

2:Dsn 3:Proto 4:Dev

2:Dev


Focused Cycle Time Reduction

Iterate until the Critical Chain is acceptable in length and content

Identify the Critical Chain

Challenge the assumptions alongthe Critical Chain

Change thenetwork to reflect new assumptions

Levelthe

Load


Step 3: Deal with Uncertainty

2 Dev

2:Dsn 3:Proto 4: Dev 2:Tst 6.5: Project Buffer

5:Design 2 Dev

2:Dsn 3:Proto 4: Dev 2:Tst

5:Design

Feeding Buffer

The Project Buffer protects the project due date from disruptions along the Critical Chain.

6.5: Project Buffer

Feeding buffers protect the Critical Chain from disruptions in non-Critical Chain tasks.

2: FB


Shorter Project

The Difference

10:Design 4:Dev

4:Tst4:Design 6:Proto 8:Dev

2 Dev


2: FB5:Design

Better Protected


2 Dev


2: FB5:Design

Today

Design: We completed the 2-day task, but we still have 4 days to go on our other task

Projected task times

Buffer consumptionProjected task time

Proto: We havent had a chance to get to our task"

Project ReportCC Complete: 15%PB Consumed: 30%

Updating Tasks


Multi-Project Scheduling

2 Dev


2: FB5:Design

1

2

1. Set projects at their due dates

3. Collect drum resource tasks5. Reschedule projects

DrumSchedule 2 Dev4: Dev 2 Dev4: Dev

2: FB5:Design 2 Dev


4. Resolve drum contention

6. Make necessary adjustments2. Select the drum resource(s)


3. Practical Recommendations

Strive for Task EngagementManage BuffersDevelop Repeatable ProcessesGate Your Projects


Task ATask BTask C

Tasks assigned to a resource

3 days3 days3 days

Should happen: Task A Task B Task C3 days 3 days 3 days

Problem: Multitasking

Does happen:

8 days

A CB CA B CA B CA


Problem: Interruptions

Phone callsConversation in the next cubicleEmailA knock on the door . . .

Minimize interruptions on key tasks!


Recommendation:Strive for Task Engagement

Minimize multitasking with clear, stable priorities

Find ways to minimize interruptions Identify key tasksPromote complementary work rules

Task Engagement: the need to focus on a task and work it to completion before being interrupted for other activities.


Recommendation: Manage Buffers

Use average but credible task durationsUse up to 50% buffer sizingCreate project buffers as explicit tasksTrack buffer consumptionReport based on buffer status


Project % Complete

Project

Buffer % Used

Project Due Date

CompleteProject Early Finish

Planning Threshold

Action Threshold

Executive Decision Support


Recommendation:Develop Repeatable Processes

Scheduling processes Credibility Risk management Buffer management

Tracking and reporting processes Buffer analysis and reports Clear, stable task priorities Cost analysis if appropriate


Recommendation: Gate Your Projects

Project charterPhase/gate processesTake into account capacity (drum resource)Maintain credibility

Typically, the company has in process twice as much work as it can staff effectively. This means that half the work is sitting idle somewhere, and each project takes twice as long as it needs to.

Preston Smith, Saying No to Customers, Across the Board, March 1994

Critical Chain

Documents

Transcript of Critical Chain