About Constraints

Constraints are recognized real-world restrictions that affect project performance. Any factor that potentially delays when an activity can be scheduled is a constraint. The most typical constraints are date restrictions. Constraints can apply to the entire project or only to individual activities and can even reflect external project requirements that cannot be built into the network logic. You can apply up to two constraints to activities in the Status detail window of the Activities page, or by dragging the start or end of a bar in the Gantt view of the Activities page.

A hard constraint prevents activities from being moved. In P6, the hard constraints available are Mandatory Start and Mandatory Finish. A soft constraint does not prevent activities from being moved, but it can distort float. In P6, the soft constraints available are Start on, Start on or before, Start on or after, Finish on, Finish on or before, and Finish on or after.

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