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Project Professional Forcing Schedule to Meet Deadline/Constraint RRS feed

  • Question

  • Hello, 

    I am using MP Professional (Desktop version, 2019). I am not new to MP, but our company is starting to utilize more tools of MP (in the past, we have kept it very simple but as we grow - need to get more in depth). 

    I have a Project that has a deadline (because it is helpful to see the ticker when the date goes past) and a Finish-No-Later than constraint on our final ship date. Our resources are over-allocated, and our Project has went past this deadline/constraint day. I would like to know how to determine what needs to be done in order to meet that deadline day and why MP is exceeding the due date when it is set as a constraint? 

    We have multiple projects/jobs within one resource pool, so it is not a simple matter of adding resources (because, I might be over-allocated in the same week on different jobs (projects) that without manually adding resources and continually checking the new ship/finish date, I am unable to get a clear picture on how to revise my schedule to meet the deadline. If the constraint date was held, this would be much easier to manipulate. 

    I would have expected MP to maintain the constraint, but show high overallocations in which we could add resources because that date is held and adding resources is what is needed to keep that date. 

    Any insight on this would be appreciated. 

    Monday, June 3, 2019 12:59 PM

All replies

  • Amber2000 --

    I would suspect that an important option has been changed in the Project Options dialog.  Click the File tab and then click the Options tab in the Backstage.  In the Project Options dialog, click the Schedule tab.  Scroll down to the Scheduling Options for This Project section and SELECT the option named Tasks Will Always Honor Their Constraint Dates.  Click the OK button.

    When the preceding option is deselected, Microsoft Project allows the constrained task to slip past its constraint date, based on task dependency relationships with Predecessor tasks.  When the option is selected, the software enforces the constraint and will not allow the task to slip past its constraint date.  Please let us know if this helps.


    Dale A. Howard [MVP]

    Monday, June 3, 2019 1:57 PM
    Moderator
  • Amber2000,

    You said: “I would like to know how to determine what needs to be done in order to meet that deadline day ….?”

    • Study and become familiar with Total Slack, Critical Tasks, and the Critical Path in a project schedule.
    • Display, examine and shorten the “Critical Path” to the final delivery milestone – by selectively modifying Critical tasks.  E.g. shorten the duration by adding resource units.  Beware that shortening the Critical Path increases the chances that other, non-critical tasks will become critical.  Overall project risk increases.
    • In case of multiple constraints and/or multiple calendars, you may find it useful to display the Driving Predecessors Task Path to each constrained milestone/delivery.
    • Project has a fairly powerful Resource Leveling module that automatically resolves overallocations by delaying less important tasks in favor of more important tasks that demand the same resources.  Your problem description mentions lots of over-allocation without mentioning leveling.  Study and become familiar with Resource Leveling in Project.

    You said: “I would like to know … why MP is exceeding the due date when it is set as a constraint?”

    • Your FNLT constraint (or Deadline) only touches the Late Finish of the constrained task and is propagated from that date to the Late dates of all the task’s predecessors.  During normal/forward scheduling, the Start/Finish dates are set equal to the Early Start/Finish dates (NOT the Late dates) of each task.  These never see the constraint.
    • If the Late dates precede the Early dates for any task, then the task’s Total Slack is negative.
    • If the “Tasks will always honor their constraint dates” box is checked (the default setting and as Dale suggested) AND Total Slack is negative, AND the negative Total Slack is caused by a Constraint (NOT a Deadline) that is applied to the task itself, THEN Project will advance the Early dates of the constrained task to match the Late dates.  This is a lie, as it forecasts meeting a date commitment that the rest of the schedule does not support. 
    • Unchecking the box – or avoiding the issue altogether by using Deadlines in lieu of SNLT/FNLT constraints – stops the lie.
    • In either case (box checked or unchecked), negative Total Slack indicates that the constraint/Deadline cannot be met as scheduled.
    • No doubt this is more detail than you wanted, but you did ask "why."

    In your last paragraph, you are expecting Project to do something that it doesn’t – i.e. automatically shortening task durations (thus “crashing” the schedule) along the driving logic path to a delivery milestone, as needed to meet the delivery constraint or Deadline.  While such behavior seems appealing to you now, there are a lot of reasons why it’s just a bad idea in the long run.  Project is still just a tool for project managers (and schedulers) to use.

    Good luck, tom


    • Edited by Tom BoyleBPC Monday, June 3, 2019 8:06 PM format
    • Proposed as answer by Rob Schneider Tuesday, June 4, 2019 7:32 AM
    Monday, June 3, 2019 8:05 PM
  • I think you are perhaps confusing input and output.

    Input is all of the tasks and their durations and their predecessors and successors.

    Output is all of the scheduled dates, including the overall earliest finish.

    If you put in all of the tasks etc and build a model that finishes overall later than desired target finish date, then you must either accept that the target is unachievable or find some way to change the inputs.

    I haven't mentioned resources. The input is the resource assignment. The output is the work. If the work is higher or lower than you would like or expect it to be, then you have to either accept it or find a way to change one of or a combination of the inputs that are causing it.

    I haven't mentioned cost. The input is the resource assignment as well as any other costs ("fixed cost"). The output is the cost. If the cost is higher or lower than you would like or expect it to be, then you have to either accept it or find a way to change one of or a combination of the inputs that are causing it.

    You can't just stick a FNLT constraint on the last task and expect MSP to tell you what the durations and resource assignments for all of the tasks should be to make it happen. It's software. It can't read your mind or manage the project for you.

    MSP has the Critical Path Method built in to the scheduling engine. If you understand the method and stick to it, planning suddenly makes a lot more sense and gets very easy.

    If I ask you to build me a house by next Tuesday afternoon but everything in the plan says that it cannot be done before the end of November, then putting a FNLT constraint on "hand over the keys" won't get the house built by next Tuesday afternoon or tell you how it can be done.

    Hope this helps a bit.

    • Proposed as answer by Rob Schneider Tuesday, June 4, 2019 7:32 AM
    Monday, June 3, 2019 11:08 PM