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Project Pro 2010 Negative Total Slack recalc "artifacts" RRS feed

  • Question

  • Hi folks,

    Just wondering if folks have seen this before in Pro 2010.  We had negative Total Slack in a schedule caused by a Deadline on a task.  The same negative slack value propagated back through that task's predecessor chain.  When I removed the Deadline, Project recalculated, and the Total Slack reverted to positive values for all but one of the predecessor tasks.  The predecessor in question retained the same negative Total Slack it had before the recalc, but with no apparent cause.  I "wiggled" the task to force another recalc or two by first decreasing the task's Duration by one day, and then increasing the Duration by one day.  After the recalcs, the negative Total Slack value on that task was replaced by an expected positive value.

    Thanks,

    lp

    Tuesday, July 2, 2013 7:29 PM

Answers

  • lp --

    It sounds like Microsoft Project 2010 did only a partial recalculation on the Total Slack values.  I have occasionally seen where the software seems to do an incomplete calculation of the schedule.  Fortunately, this event is very rare.  But when it does happen, I usually press the F9 function key to force a recalculation, and then this takes care of the problem.

    In addition, the negative Total Slack situation you encountered is normal.  When you miss either a Deadline date or an inflexible constraint date (such as on a Finish No Later Than constraint), the software does generate negative total slack for every task that is a predecessor for the task that missed the date.  This also caused the software to format the Gantt bars of all of those tasks in red, as if they are Critical tasks.  Hope this helps.


    Dale A. Howard [MVP]

    • Marked as answer by linearprism Tuesday, July 2, 2013 8:32 PM
    Tuesday, July 2, 2013 7:35 PM
    Moderator

All replies

  • lp --

    It sounds like Microsoft Project 2010 did only a partial recalculation on the Total Slack values.  I have occasionally seen where the software seems to do an incomplete calculation of the schedule.  Fortunately, this event is very rare.  But when it does happen, I usually press the F9 function key to force a recalculation, and then this takes care of the problem.

    In addition, the negative Total Slack situation you encountered is normal.  When you miss either a Deadline date or an inflexible constraint date (such as on a Finish No Later Than constraint), the software does generate negative total slack for every task that is a predecessor for the task that missed the date.  This also caused the software to format the Gantt bars of all of those tasks in red, as if they are Critical tasks.  Hope this helps.


    Dale A. Howard [MVP]

    • Marked as answer by linearprism Tuesday, July 2, 2013 8:32 PM
    Tuesday, July 2, 2013 7:35 PM
    Moderator
  • Thanks, Dale.  I bumped into this twice in two different schedules (from the same group of schedules with linked predecessors and successors) about an hour apart, that's why I was asking.

    lp

    Tuesday, July 2, 2013 8:34 PM