This constraint indicates the exact date that a task must begin. Other scheduling parameters, such as task dependencies, lead or lag time, resource leveling, and delay, can't affect scheduling the task unless this requirement is met. This constraint indicates the exact date that a task must be completed. Other scheduling parameters, such as task dependencies, lead or lag time, resource leveling, and delay, can't affect scheduling the task unless this requirement is met. Slack Critical tasks have no slack and noncritical tasks do have slack, meaning they have buffer time available, so their start or finish may be delayed without affecting the start of any successor tasks.
Free slack is the amount of time a task can slip before it delays another task.
Total slack is the amount of time a task can slip before it delays the project finish date. When the total slack is negative, the task duration is too long for its successor to begin on the date required by a constraint, or a successor has actual start and finish dates, or actual durations, entered which conflict with the constraint date. If a noncritical task consumes its slack time, it usually causes its successor to use some or all of its total slack time. The task becomes a critical task and causes its successor tasks to become critical as well, once the successor's total slack equals zero. Total slack is calculated by comparing the minimum of the difference between the late start date and early start date and the difference between the late finish date and early finish date.