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Predecessors do not honor time constraint

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  • #410475

    Dear people,

    It took quite some time, but I finally made an overall planning in MS project 2013 with all the tasks neatly linked together with a FS link. For my client, i’m looking to show the Gantt chart with the last action just before the deadline date so I can set this as my baseline.

    The problem is that whenever I manually schedule the last task (or add a time constraint to ‘finish no later than’), the last task jumps to the deadline date, but all the predecessors stay put. This leads to the confusing situation where the predecessors are later than the deadline date, eventhough they are FS linked.

    What can I do so that the predecessors slide in front of the last task, so that my whole project honors the deadline date?

    Thank you in advance.

    Sai Prasad
    • Community Leader
    • Forum Pro

    Hi Luc, It looks like though FS dependency type is set between tasks the last task jumps to the deadline date. Based on the observations stated make the following changes (if not done) in the same sequence
    1. Change the Task Mode to all tasks to Auto Scheduled
    2. In Project Information (via Project tab), change the “Schedule From” drop down from “Project Finish” to “Project Start”. This will will ensure all new tasks in this plan are scheduled “As Soon as Possible” from Project Start and predecessor set
    3. Insert Constraint Type field in Gantt Chart view. If the “Schedule From” was set initially to “Project Finish”, then all tasks will be scheduled by default as “As Late As Possible”. Change the Constraint Type values of all tasks to “As Soon As Possible”

    Do you have any work resources assigned to these tasks? If you could provide a link to the screenshot it would help us to troubleshoot and give recommendations.

    Tom Boyle

    Luc, Sai Prasad’s recommendations are excellent. In addition, note the status of the checkbox for “Tasks will always honor their constraint dates” in the Schedule Options (under “Scheduling options for this project”.) The box is checked by default, allowing tasks with late constraints (but not their predecessors) to violate the scheduling precedence logic. This is what you have observed. Un-checking the box restores the primacy of the logic, which is more consistent with other project scheduling tools.

    The behavior you would like to see – automatic acceleration of all tasks necessary to meet a constraint – is not something that Project does. Instead, all the tasks needing acceleration have negative Total Slack and are automatically marked Critical. You can alleviate the negative slack by starting the project earlier, by crashing (shortening task durations), or by fast-tracking (overlapping some tasks). These are project management decisions best not left to software.

    Sai Prasad
    • Community Leader
    • Forum Pro

    Thank you Tom. Thanks for adding another insight on the checkbox “Tasks will always honor their constraint dates”. In Luc’s message, it is mentioned for the last task the constraint type is set to “Finish No Later Than” and for me it looks like Deadline field is not used rather Constraint Type set to Finish No Later Than is used. Also, setting the behavior of FS dependency type changed on whether the project is forward or backward scheduled.

    My suggestion is
    1. Change the Schedule From: to Project Start in Project Information dailog
    2. Change the Constraint Type of all tasks to As Soon As Possible
    3. Set Deadline (Advanced Tab) to deadline date on the last task. If the last task misses the Deadline date, you will get alert in Indicator column https://support.office.com/en-us/article/Deadline-task-field-8c6c4acd-1324-484a-a92b-9bd2eb313dfa

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