Critical Chain Project Management


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Pitfalls in traditional project scheduling and execution - solution: Critical Chain

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  • Critical Chain Project Management

    1. 1. Critical Chain Project Management Fred Wiersma TTI-30 June 2000
    2. 2. Contents <ul><li>Problems with traditonal scheduling methods </li></ul><ul><li>Solutions for these problems </li></ul><ul><li>Single project and multi projects environment </li></ul>
    3. 3. Problems with traditional scheduling methods <ul><li>Single project </li></ul><ul><li>Multiple projects </li></ul>
    4. 4. Single project problems <ul><li>Tasks duration estimated using 90 + % chance of completion </li></ul><ul><ul><li>“ I think this should take 5 days, but let me estimate 8 days - I am sure to complete it within 8 days” </li></ul></ul><ul><li>Effect: safety built-in on task basis </li></ul>
    5. 5. Single project problems (2) <ul><li>Student syndrome - start too late </li></ul><ul><ul><li>“ well, I have 8 days, first I'll do some non-project work; is more fun & also useful” </li></ul></ul><ul><li>Effect: remember your school days… Who starts on time? </li></ul>
    6. 6. Single project problems (3) <ul><li>Parkinsons Law: work fills available time for a task </li></ul><ul><ul><li>(after 5 days:) ”I am almost finished with this task. The remaining days I can build some bells & whistles for this module. Or improve the GUI. Or ...” </li></ul></ul><ul><li>Effect: tasks always fill the time scheduled - never less. </li></ul>
    7. 7. Single project problems (4) <ul><li>The 3 minute Egg Syndrome </li></ul><ul><ul><li>“ How can you be ready in 4 days when 8 days were estimated? Did you forget something? What about the quality of your work?“ </li></ul></ul><ul><li>Effect: people don’t get rewarded for completing tasks early. </li></ul>
    8. 8. Single project problems (5) <ul><li>Multitasking </li></ul><ul><ul><li>“ I am busy with A & B, and should be working on C too.” </li></ul></ul><ul><li>Effect: all tasks take more time: instead of 3 x 3 days, 3 x 4 days is more probable due to task switching </li></ul>
    9. 9. Single project problems: Summary <ul><li>Safety on task level, not on project level </li></ul><ul><li>Student syndrome - start too late </li></ul><ul><li>Work fills available time </li></ul><ul><li>Early finish not rewarded </li></ul><ul><li>Multitasking </li></ul>
    10. 10. Example: Bad Multitasking Task A Task B Task C Tasks assigned to a resource 3 days 3 days 3 days Should happen : Task A Task B Task C 3 days 3 days 3 days Could happen: B B A A C C 6 days 6 days 6 days Does happen : B B A A C C 7 days 7 days 7 days Lost Productivity
    11. 11. And some more… <ul><li>Say a task is scheduled for 8 days, takes 5 days. Can the next task be started right away? Or is the resource not yet available? </li></ul><ul><li>Even worse if the task takes more than 8 days. Will the resource for the next task be available longer? </li></ul>
    12. 12. And more... <ul><li>Rescheduling occurs frequently, which lowers confidence in schedule to team members and stake holders </li></ul>
    13. 13. What can we do? <ul><li>Move safety from task level to project level. </li></ul><ul><li>Prevent multitasking - assign priorities. When starting on a task, proceed till finish. DO NOT multitask. </li></ul>
    14. 14. Identify the Critical Chain <ul><li>B.) Identify the Critical Chain </li></ul>The Critical Chain The longest path through the network considering both task and resource dependencies A.) Eliminate resource contention 2:Dev 2:Tst 5:Design 2:Tst 2:Dev 2:Dsn 3:Proto 4:Dev 2:Dsn 3:Proto 4:Dev 2:Dsn 3:Proto 4:Dev
    15. 15. Rules of thumb <ul><li>divide safe task estimates in 2 - half of half of the estimate goes into the project buffer </li></ul><ul><li>define feeding buffers for tasks prior to crtitical tasks </li></ul><ul><li>define resource buffers as a ‘wake up’ call to assure resource availability </li></ul>
    16. 16. Manage the Project Buffer Okay Plan Act 0% 33% 66% 100% Percent Buffer Consumed Percent Critical Chain Remaining 100% 67% 33% 0% Manage on buffer status with respect to work completed
    17. 17. Rules of thumb (3) <ul><li>Daily update project status with estimate to complete for each resource </li></ul>
    18. 18. Updating Tasks Design : “ We completed the 2-day task, but we still have 4 days to go on our other task” Proto : “ We haven’t had a chance to get to our task&quot; Project Report CC Complete: 15% PB Consumed: 30% Copyright © 1999 by ProChain Solutions, Inc. All rights reserved. 2 Dev 2:Dsn 3:Proto 4: Dev 2:Tst 6.5: Project Buffer 2: FB 5:Design Today Projected task times Buffer consumption Projected task time
    19. 19. The Multi-Project Solution <ul><li>Schedule individual projects using critical chain </li></ul><ul><li>Determine the timing of individual projects using a drum schedule </li></ul><ul><ul><li>Resolve resource contention on the most heavily loaded resource across all projects </li></ul></ul><ul><ul><li>Paces the start of new projects </li></ul></ul>Copyright © 1999 by ProChain Solutions, Inc. All rights reserved.
    20. 20. Multi-Project Scheduling 1 2 1. Set projects at their due dates 3. Collect drum resource tasks 5. Reschedule projects Drum Schedule 4. Resolve drum contention 2. Select the drum resource(s) 2 Dev 2:Dsn 3:Proto 4: Dev 2:Tst 6.5: Project Buffer 2: FB 5:Design 2 Dev 2:Dsn 3:Proto 4: Dev 2:Tst 6.5: Project Buffer 2: FB 5:Design 2 Dev 4: Dev 2 Dev 4: Dev 2 Dev 4: Dev 2: FB 5:Design 2 Dev 2:Dsn 3:Proto 4: Dev 2:Tst 6.5: Project Buffer 2 Dev 4: Dev
    21. 21. References <ul><li>Books: </li></ul><ul><ul><li>Eliyahu M. Goldratt - Critical Chain (Business novel on project management) – ISBN 0-88427-153-6 </li></ul></ul><ul><ul><li>Robert C. Newbold - Project Management in the Fast Lane - ISBN 1-57444-195-7 - discusses CCPM in a ‘how to’ manner. </li></ul></ul>
    22. 22. References(2) <ul><li>Websites: </li></ul><ul><ul><li> - Info on Theory of Constraints and CCPM </li></ul></ul><ul><ul><li> - Crazy about Constraints - articles, books references, lots of links </li></ul></ul><ul><ul><li> - supplier of CCPM add-on to MS Project </li></ul></ul>