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Loss of critical path after resource leveling in Project Professional 2007. RRS feed

  • Question

  • Hello friends

    I have a question regarding the critical path and its not showing after leveling resources.

    Loss of sight of the critical path, represented by activities with red bars, and should establish a link between the early completion of the project, this fact did not occur just after the leveling of resources.



    Hezequias Vasconcelos


    Friday, June 29, 2012 11:51 AM

Answers

  • From a theoretical standpoint, the critical path is no longer valid in a resource constrained environment.  I think Eric Uyttewaal's book on Forecast Scheduling has a nice, long discussion about it.  In that case, you would want to look at the Resource Critical Path - for which he's got both a technique and a macro (that both come with the book).


    Andrew Lavinsky [MVP] Blog: http://azlav.umtblog.com Twitter: @alavinsky

    Tuesday, July 3, 2012 2:03 AM
    Moderator
  • Hezequias --
     
    Assuming you have the Critical Path displayed in the Gantt Chart view, click View > Tables > Schedule.  With the Schedule table now displayed, drag the split bar to the far right side of the Total Slack column.  Do you see any incomplete tasks that have 0 Days of Total Slack?  Compare these to the Gantt bar for each of those tasks.  Are the Gantt bars red or blue?  If you see a Total Slack value greater than 0 days for any task, this means that the task is no longer a Critical task, and will show a blue Gantt bar instead of a red Gantt bar.  Let us know what you find.

    Dale A. Howard [MVP]
    VP of Educational Services
    msProjectExperts
    http://www.msprojectexperts.com
    http://www.projectserverexperts.com
    "We write the books on Project Server"

    Friday, June 29, 2012 10:21 PM
    Moderator
  • Hello,

    Critical path is basically set of tasks which impact the Finish Date of the Project directly; so as Dale noted that all tasks with 0 slack should fall on a Critical path, i.e. they cannot be delayed without impacting Project Finish Date.

    But critical path keeps changing as we progress in a project schedule based on various factors, like the 1 you noted - Resource Leveling. So, it is possible sometimes that the Critical Path gets changed after leveling. You have option to define when a task be considered Critical based on Slack value, so if scenario arise you can use this option to adjust your Critical Path.


    Sapna S

    Tuesday, July 3, 2012 12:40 PM
    Moderator
  • I would say also that the critical path method, the critical path and critical tasks, strictly speaking, are all about scheduling by using a network of tasks for which the only information needed is the duration estimate of the tasks and the predecessor/successor relationships between all of the tasks and all of the other tasks in the network. It starts with the assumption that nothing else, including resource limitations, is a factor. It therefore assumes that resources, whatever they may be, are unlimited and readily available. This is a reasonable assumption to start with because, with very little information and some careful modelling, it produces the vital information about the absolute earliest possible start and finish date/time, and the absolute latest start and finish and the free slack and the total slack of each task. It answers the question which is "how fast can this be done if we have unlimited or readily available resources, which is a good thing to know. Anything which then re-schedules a task after that first step to a later (it must be later) earliest start and finish will change the apparent critical path simply because it changes the result of the calculation of slack. Resource limitation is not the only thing that does it. Date, constraints, leveling, resource calendars also do it. Also, setting deadlines changes the way that slack is calculated. Also, whether you choose in calculation options to show just one or multiple critical paths changes the way that slack is calculated. And although the definition of critical is usually 0 total slack, even that can be changed.
    When I level, I always start with "level only within available slack", which ensures that the CP stays where it was.

    Wednesday, July 4, 2012 5:28 AM

All replies

  • Hezequias --

    Display the Gantt Chart view with your Critical Path applied.  Click View > Tables > Schedule and pull the split bar to the right side of the Total Slack column.  For every incomplete task with a Total Slack of 0 days, you should see the Gantt bar is formatted in red.  For every incomplete task with a Total Slack > 0 days, you should see the Gantt bar formatted in blue.  Is that what you see?  Let us know and we will try to help.


    Dale A. Howard [MVP]
    VP of Educational Services
    msProjectExperts
    http://www.msprojectexperts.com
    http://www.projectserverexperts.com
    "We write the books on Project Server"

    Friday, June 29, 2012 6:51 PM
    Moderator
  • Hezequias --
     
    Assuming you have the Critical Path displayed in the Gantt Chart view, click View > Tables > Schedule.  With the Schedule table now displayed, drag the split bar to the far right side of the Total Slack column.  Do you see any incomplete tasks that have 0 Days of Total Slack?  Compare these to the Gantt bar for each of those tasks.  Are the Gantt bars red or blue?  If you see a Total Slack value greater than 0 days for any task, this means that the task is no longer a Critical task, and will show a blue Gantt bar instead of a red Gantt bar.  Let us know what you find.

    Dale A. Howard [MVP]
    VP of Educational Services
    msProjectExperts
    http://www.msprojectexperts.com
    http://www.projectserverexperts.com
    "We write the books on Project Server"

    Friday, June 29, 2012 10:21 PM
    Moderator
  • Hello Dale.

    At the moment I am unable to access and test information in the schedule of Project 2010 the only print that I have to show you my problem I could not insert into the body of the thread.


    Hezequias Vasconcelos


    Saturday, June 30, 2012 11:23 AM
  • Hezequias --
     
    Let us know what you find when you can open and test the project.
     

    Dale A. Howard [MVP]
    VP of Educational Services
    msProjectExperts
    http://www.msprojectexperts.com
    http://www.projectserverexperts.com
    "We write the books on Project Server"

    Saturday, June 30, 2012 11:42 AM
    Moderator
  • From a theoretical standpoint, the critical path is no longer valid in a resource constrained environment.  I think Eric Uyttewaal's book on Forecast Scheduling has a nice, long discussion about it.  In that case, you would want to look at the Resource Critical Path - for which he's got both a technique and a macro (that both come with the book).


    Andrew Lavinsky [MVP] Blog: http://azlav.umtblog.com Twitter: @alavinsky

    Tuesday, July 3, 2012 2:03 AM
    Moderator
  • Hello,

    Critical path is basically set of tasks which impact the Finish Date of the Project directly; so as Dale noted that all tasks with 0 slack should fall on a Critical path, i.e. they cannot be delayed without impacting Project Finish Date.

    But critical path keeps changing as we progress in a project schedule based on various factors, like the 1 you noted - Resource Leveling. So, it is possible sometimes that the Critical Path gets changed after leveling. You have option to define when a task be considered Critical based on Slack value, so if scenario arise you can use this option to adjust your Critical Path.


    Sapna S

    Tuesday, July 3, 2012 12:40 PM
    Moderator
  • I would say also that the critical path method, the critical path and critical tasks, strictly speaking, are all about scheduling by using a network of tasks for which the only information needed is the duration estimate of the tasks and the predecessor/successor relationships between all of the tasks and all of the other tasks in the network. It starts with the assumption that nothing else, including resource limitations, is a factor. It therefore assumes that resources, whatever they may be, are unlimited and readily available. This is a reasonable assumption to start with because, with very little information and some careful modelling, it produces the vital information about the absolute earliest possible start and finish date/time, and the absolute latest start and finish and the free slack and the total slack of each task. It answers the question which is "how fast can this be done if we have unlimited or readily available resources, which is a good thing to know. Anything which then re-schedules a task after that first step to a later (it must be later) earliest start and finish will change the apparent critical path simply because it changes the result of the calculation of slack. Resource limitation is not the only thing that does it. Date, constraints, leveling, resource calendars also do it. Also, setting deadlines changes the way that slack is calculated. Also, whether you choose in calculation options to show just one or multiple critical paths changes the way that slack is calculated. And although the definition of critical is usually 0 total slack, even that can be changed.
    When I level, I always start with "level only within available slack", which ensures that the CP stays where it was.

    Wednesday, July 4, 2012 5:28 AM
  • Hello Friends,

    Thanks for me help.


    Hezequias Vasconcelos

    Wednesday, July 4, 2012 2:08 PM
  • You are most Welcome!!

    Sapna S

    Wednesday, July 4, 2012 3:33 PM
    Moderator