Critical Path and Negative Total Slack

[BoanHed]

I have got a large project file that I am working on which is of 2200 lines and am having some problem getting a true representation of my critical path. I checked that many of the tasks on the critical path are having very high negative total slack values and also that many of these tasks have started already/ Can anyone tell me whether there is a a relationship between a task starting and negative total slack? What I mean to ask is that, does a tasks Actual Start create an inflexible constraint date that somehow triggers negative total slack in some or all of its dependencies? Will the negative total slack mean I have to start that many days earlier for the task in order not to delay the project? Thanks for any help.

[Anywhere]

Actually, the negative slack will show the amoun of time which must be saved so that successor tasks are no displayed. This negative slack tells us that there is not enough time scheduled for the task and it is usually created by constraint dates or task dependencies. The field is available only in the Bar Styles dialog box and is represented as a bar on the Gantt Chart. The total slack is then calculated as the smaller value of the late finish field minus the early finish field and the late start field minus the early start field. You can try to add the negative slack field as a Gantt bar style when you want to indicate graphically on the gantt chart amount of negative slack for tasks.

[Viceman]

Incase the 2 tasks are linked then the second tasks gets an actual start date which will be earlier than originally scheduled, then the first task gets a negative Total Slack telling us that it should have finished earlier. So, after the first task is completed 100%, then its total slack becomes zero. Another way the task can get negative slack is if a finish date is forced on a task earlier than if all links were obeyed. You can try to remove all constrained dates on tasks except for valid date constraints.

[Actionguy]

The other things that can cause negative slack, as well as date constraints on tasks which make them earlier than their predecessors would otherwise allow is Deadlines. Deadline is not a useful indicator with a pretty green arrow on the Gantt Chart while they finish earlier than the Deadline. But after once they go past the Deadline, then Microsoft Project gives them negative lag to the amount late, so you should not use them.