What is a Microsoft Project Scheduling Constraint?
In Microsoft Project constraints can be used to create a link between a task and a particular date. By choosing a Constraint Type you can set how Microsoft Project constrains the start or finish dates of a given task. stakeholdermap.comBy default all tasks are created with the Constraint type 'As Soon As Possible'. This allows Microsoft Project to schedule a task on the basis of its duration, resource(s) and dependencies, rather than against a particular date.
What are the Constraints types in Microsoft Project?
There are eight constraint types in Microsoft Project:- As Soon As Possible (ASAP)
- Flexibility: Flexible
- Description: Default for projects scheduled from start date. Starts ASAP, considering dependencies.
- As Late As Possible (ALAP)
- Flexibility: Flexible
- Description: Default for projects scheduled from finish date. Tasks start as late as possible without delaying others.
- Finish No Earlier Than (FNET)
- Flexibility: Moderately flexible
- Description: Can't finish earlier than a specified date, but it can finish any time after.
- Finish No Later Than (FNLT)
- Flexibility: Moderately flexible
- Description: Can't finish later than a specified date, but it can finish any time before.
- Must Finish On (MFO)
- Flexibility: Inflexible
- Description: Task must finish on a specific date.
- Must Start On (MSO)
- Flexibility: Inflexible
- Description: Task must start on a specific date.
- Start No Earlier Than (SNET)
- Flexibility: Moderately flexible
- Description: Task can't start earlier than a specified date, but it can start any time after.
- Start No Later Than (SNLT)
- Flexibility: Moderately flexible
- Description: Can't start later than a specified date, but it can start any time before.
Why would you set a Constraint?
Sometimes you need to prevent Microsoft Project from rescheduling a task away from a key date. For example, imagine you are managing the delivery of a conference. The date of the conference is likely to have been booked for months and is probably immovable. In this instance you might set a ‘Must start on’ project constraint for the date of the conference.
Assuming ‘Conference day’ has other tasks linked to it, MS Project will warn you that a constraint might cause a future scheduling conflict. That is fine because if one of the tasks linked to the Conference day takes longer than planned then we need to know if it will conflict with the Conference start date.
Planning Wizard constraint warning. Text and options
You set a Must Start On constraint on the task 'Task 2'. This could result in a scheduling conflict either now or later because this task has at least one other task linked to it.
You can:
- Cancel. No constraint will be set on 'Task 2'.
- Continue, but avoid the conflict by using a Start No Earlier Than constraint instead.
- Continue. A Must Start On constraint will be set.
How Microsoft Project warns you if a constraint will create a scheduling conflict
Lets say that Arranging the AV equipment was planned to take 2 days, but we find that actually it will take 6 days. If we increase the duration to 6 days Microsoft Project will warn us that there is a scheduling conflict (see below).
Planning Wizard scheduling conflict warning. Text and options.
This action will cause a scheduling conflict. Task 14 of 'constraints-in-microsoft-project.mpp' has a task constraint or is linked to a task that cannot move, and as a result the constraint or the link cannot be set.
You can:
- Cancel. Avoid the scheduling conflict.
- Continue. Allow the scheduling conflict.
So Project Constraints can be useful and have a valid part to play in project planning. However, they can also be created by mistake with dangerous knock on effects. In part 2 see how accidentally setting constraints can impact your project plan.
What does a Task Constraint look like?
You can tell if a task has a constraint by checking the Indicator column in the task table. This is usually visible, but if not click on the Task Name column and select Insert Column. Then select Indicators from the dropdown.To see more details you can add the Constraint Type and Constraint Date columns to your task table.
You can also see the Constraint Date and Type by hovering over the Constraint icon in the Indicators field. A tooltip will appear reading 'This task has a [constraint type] constraint on [date].'
Project Constraints part 2 - common mistakes.
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Read more guides on using Microsoft Project
- Project Calendars - Non-working time - enter UK holidays into Microsoft Project calendars
- Constraints part 1 - How to use Microsoft Project constraints
- Constraints part 2 - Common mistakes in using constraints
- Create constraints - How to create project constraints
- Critical Path - Viewing the Critical Path - video tutorial
- Filters - How to filter your plan by certain tasks or resources
- Filters - How to create a custom filter in Microsoft Project
- Highlight tasks - This step by step guide shows how to highlight particular tasks in Microsoft Project.
- Hyperlinks - How to create hyperlinks in Microsoft Project
- Outlook tasks - How to import Outlook tasks into Microsoft Project
- How to create a PDF of your project plan - Microsoft Project 2010 to pdf
- Scheduling problems - How to resolve a common scheduling problems in Microsoft Project