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
Scheduling Constraints - Tutorials and Articles
Browse these tutorials and articles with a focus on Scheduling Constraints and Primavera P6.