New tasks being created with zero slack – why might that happen?

[Dan Schaeffer]

I have a sub-project in which any new task I create gets zero slack and is therefore critical – regardless of length. This is true for tasks with no constraints or dependencies. Why might that be happening? How might I fix this?

[Dan Schaeffer]

Just a quick edit to be able to check the ‘notify me of follow-up replies via email’

[Daryl Deffler]

Dan
In order for Project to determine which tasks are on the critical path, all tasks need to have predecessor and successor tasks. Slack is the amount of time a task can be delayed without impacting the project end date. If a task has no predecessor/successor tasks, project can’t assess the delay impact and therefore can’t determine a slack value. So it becomes zero.
It may not really be critical path in terms of how you or I would assess it, but simply based project’s binary logic (<1 = critical_) it shows flagged as critical. I’ve seen projects with many dozens of unlinked tasks showing as critical. In addition, I’ve also seen many smaller task chains showing as critical simply because the task chain is missing a first task in chain predecessor and/or last task in chain successor.
Create a view to include any tasks with null predecessor and/or successor values and add the missing dependency to all identified tasks until all tasks (except first and last) have both. That should take care of the issue.

Hope that helps

[Dan Schaeffer]

Daryl,

Thanks for pointing me toward a line of inquiry. I’ve got 28 tasks in this composite project which lack dependencies. Eight of them have total slack of 0, the rest are non-zero or non-zero with a question mark because the duration is not yet determined. Only 3, all from the same sub-project, are being drawn red (critical), the rest are blue. In fact every task without dependencies from that sub-project are critical.

I’ll puzzle on this some more but you’ve given me something to chew on.

Thanks,
Dan

[Thomas Boyle]

Dan, just a guess, but is the “Calculate multiple float paths” advanced option checkbox checked for some subprojects and not for others? If the checkbox is checked, then incomplete tasks lacking successors normally get a total slack of zero. If it is unchecked, then the total slack will be the difference between the task’s early finish and the early finish of the last task in the (sub)project.

[Dan Schaeffer]

Thomas,

Turned out to be a case of flat-out DB corruption. I could insert a new task at line 1 of sub-project #2 and it would have zero slack and be critical. If I created the same task at line 25, it wouldn’t. If I moved the non-critical task at line 25 up to line 1 it would become critical. I observed other situations in which a task had a simple dependency yet its start date didn’t reflect that dependency at all (it remained set at the project start date). I just decided sub-projects were not worth the hassle and broke the links.

Thanks for your help though!
Dan

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