How to reschedule tasks with constraints applied to them

This question, together with an associated data file comes from Bruce Tiven of Westerly, Rhode Island, USA:

I have a project scheduled out between mid-September and early April.

The project actually got under way a little more than three weeks late and now I would like to change the dates at the top of the chart without having to completely re-do the entire schedule. I tried changing the "Start Date" in the project information box, but it doesn't change anything.
Is there a way to simply shift the dates at the top of the chart to reflect more accurately the start and the progress of this project?

As Bruce’s sample data file contains tasks that do not possess any dependency links and merely have start constraints associated with them, his problem can be addressed in two different ways:

• As all the tasks have Start No Earlier Than (SNET) constraints applied to them, changing the project’s start date will have no effect because the tasks are individually constrained. The quick fix to this problem is to use the ‘Adjust Dates’wizard. This can be found on the ‘Analysis’ toolbar (View..Toolbars..Analysis). All Bruce has to do is enter in the revised project start date within this dialog box, and all tasks will be offset by the difference between the original start date and the revised start date.
• A more considered approach to Bruce’s problem is to question the need for SNET dates against all the project’s tasks. From my experience, constraints should be used sparingly. A simple rule to apply is to ask why a task should occur when it does. If it has to start or end due to external factors (a client signoff, access restrictions etc.), then these factors are ideal uses for constraints. If the reason is because a preceding task must be finished first (e.g. you can’t proof read a document until it has been written), a constraint alone is not applicable. A much more dynamic way to schedule (and to let Microsoft Project’s calculation engine do its job) is to create dependency links between tasks. By having these precedence links in place, any delay to a predecessor (or the project start date for that matter) will have a direct effect on all successor tasks. What’s more, a project’s Critical Path and any Total Slack or Free Slack against specific tasks is much more visible, and as such a project is much easier to manage.

When applying a constraint, choose which constraint type is most appropriate before applying the constraint. Avoid the temptation to simply enter in dates within the ‘Start’ cell for each task or to drag task bars around the Gantt chart. Either of these actions will create a SNET constraint. The Advanced Tab of the Task Information dialog or the Constraint Dates table are ideal places to add and edit constraints. Remember, if you have constraints against tasks, check their validity on a regular basis and edit constrained dates as necessary.

In conclusion, use links wherever possible and only apply constraints to tasks when there is a valid reason to do so.

Notes for Project Mentor users

See "Reference E2.2 applying task constraints" for a comprehensive explanation about this topic.

Posted by Andy Jessop