How Task Type Impacts Schedule Calculations

Changing a task property impacts other properties of a task, based on the task type of the task being updated.

Each of the five PPM task types (Fixed Duration, Fixed Duration - Effort Driven, Fixed Units(resource allocation), Fixed Units - Effort Driven, and Fixed Work) behave differently when properties are edited. Note: Depending on where you are setting the task type, this may appear as a pick list of 5 options, or a pick list of 3 options with an additional Effort Driven property.

When you change a task property (units, work or duration), other properties are recalculated to reflect the impact of the change on the schedule. Task type determines which properties are adjusted.

Note: Task type persists. This means that when you select a particular task type while adding a task, this becomes the default task type when you create tasks.

How task properties are calculated

When you change a task property, the other properties are recalculated using the equation:

Planned Work = Duration x Units

where:

Planned Work = Estimated total number of hours of work to complete the task
Duration = Difference between the task start and end dates
Units = The percentage of a resource’s time spent working on the task (Resource Allocation Units)

Impact of Task Type on the calculation

Task type defines which task property remains fixed in the calculation:

Fixed Units—Task resource allocation units are fixed and changes to planned work or task duration do not change task units. Select Fixed Units when the resources assigned to a task will not change.
Fixed Work—Planned work is fixed. Changes to task units or duration do not change planned work. Select Fixed Work when the amount of planned work for a task will not change.
Fixed Duration—Task duration is fixed. Changes to task units or planned work do not change task duration. Select Fixed Duration when the task duration will not change. For example, the task represents an all-day training session.
Effort Driven—The amount of work remains constant for a task.
Adding or removing assignees decreases or increases the task duration.
See Assignments and Effort Driven Tasks.
When the task is Fixed Duration - Effort Driven, adding or removing assignees decreases or increases the Resource Allocation units for the assignees. See Assignments and Fixed Duration - Effort Driven Tasks.

Note: Due to the way that effort driven tasks are adjusted, you should not use them for long-running tasks that have large numbers of assignees. For these types of "maintenance" tasks, use non-effort driven tasks.

What Happens When I Change a Task Property?

When you change a task property such as task duration, other properties are changed based on the task type including whether the task is effort-driven. The table below outlines what happens when certain properties are changed for each task type:

Task Type	Change Task Property
Task Type	Duration Increases	Planned Work Increases	Resource Units Increase	Add Resource
Fixed Units -Effort Driven	Planned work increases	Duration increases	Duration decreases	Duration decreases
Fixed Duration - Effort Driven	Planned work increases	Resource Units increase	Planned work increases	Resource Units decrease
Fixed Work - Effort Driven	Resource Units decrease	Duration increases	Duration decreases	Duration decreases
Fixed Units	Planned work increases	Duration increases	Duration decreases	Planned work increases
Fixed Duration	Planned work increases	Units increase	Planned work increases	Planned work increases