Part 2 Project Constraints

Common mistakes in using Project Constraints

This guide is continued from Part 1 Project Constraints - what they are and how to use them

Accidental constraints

Constraints can be set in a few ways including:

1. clicking on a task, selecting the Advanced tab and setting the constraint type and date.
2. manually setting or changing start or finish dates
3. copying and pasting tasks and including their start and finish dates

Manually setting or changing a start or finish dates

MS Project and other project planning software is designed to carry out complex calculations that Project Managers used to have to do by hand. The idea is that you input:

• what you need to do,
• in what order you need to do it and
• how long it will take.

The software will then calculate start and end dates and the critical path for the project. Project Managers who are new to MS Project will often try to set start and end dates themselves. This breaks the calculations and creates constraints against the tasks.

The simple project plan below has a project start date of 11/01/2010 and an end date of 12/02/2010.

All of the tasks have finish to start relationships and there are no constraints. The problem is the launch day has to be on the 11/02/2010. The venue is already booked and the press releases have gone out. This should prompt the Project Manager to investigate legitimate ways to reduce timescales.

However, it can be tempting simply to force the plan to meet the deadline, by changing the start and end dates. Firstly the Project Manager changes the start date to 10/02/2010.

If they are using Project 2007 they will get a warning message.

If they continue the link to the tasks predecessor ‘Train users’ will be removed and in this case a ‘Start No Earlier’ than 09/02/2010 constraint is set.

Here the existence of the constraints is less of a problem than the fact that the Project Manager is attempting to squeeze a task that takes 2 days into 1 day. Unless they take some other action to reduce the duration of the task the deadline probably won’t be met. In addition the dependency between ‘Train users’ and ‘Prepare for launch’ has been lost, this means that even if the Project Manager found a legitimate way to reduce duration earlier in the plan the reduction would not be reflected in the start date of ‘Prepare for launch’.

I have seen numerous examples of project plans that are riddled with constraints. If you see this you should be concerned. It suggests that the Project Manager may have attempted to force the plan to meet impossible deadline

Copying and pasting project tasks

This example is from a project plan produced by one of my clients.

Here the Project Manager copied and pasted the tasks, causing a series of ‘Start No Earlier’ constraints to be set. The problem here is that the tasks won’t respond to improvements in the schedule. For example ‘Tester Training’ is dependent on ‘Updating Training Materials’ which has a planned duration of 10 days. If the client had found a way to reduce the time it took to update the training materials from 10 days to 7 days then tester training could start earlier. However, because of the ‘Start No Earlier’ constraint ‘Tester Training’ will remain scheduled to start on 16/03/2010 and the improvement won’t impact the plan.

The next time you are working with a supplier or client check their project plan and look out for the constraints. There may be a problem if you see:

1. several tasks, one after the, other all with constraints against them.
2. several constraints dotted about the plan

Removing all Project Contraints automatically

Jack Dahlgren has written a macro which removes all contraints in MS Project automatically. See Working with Schedules and Constraints

How to create a Project Constraintt