The buffer used in the drum schedule to buffer the use of the drum resource in one project to its use in the next project. The net result of the capacity constraint buffer is to sequence the start of projects, rather than start them all at once.
Capacity Constraint Buffer – Is established to maintain the schedule of a constraint resource handling multiple projects. It ensures that all the required project activities are completed, before the constraint resource begins a scheduled specific activity. The scheduling becomes complicated when there are several constraint resources handling multiple projects.