primavera p6 supports 2 types of constraints; hard constraints and soft constraints.
in primavera p6, “mandatory” constraints are hard constraints. hard constraints stand out because they can break relationships. an activity that has a mandatory start or finish date becomes fixed to that date. relationships to that activity are ignored – the activity will not move even if its predecessors push it out.
all of p6’s other constraints are considered soft constraints. a soft constraint is one that p6 will try to adhere to, but relationships take priority, and may result in the constraint not being met.
