Duration Types in Primavera P6

Duration Type is a setting which allows the user to control how the duration, resource units, and resource units/time are synchronized for activities, so that the following equation is always true:

Original, Remaining or Planned Duration = (Budgeted, Remaining or Planned Units) / (Budgeted, Remaining or Planned Units/Time)

If the activity is not started, the names of the values are : Original Duration x Budgeted Units/Time = Budgeted Units
If the activity has started, the names of the values are    : Remaining Duration x Remaining Units/Time = Remaining Units
The following table lists the value that changes to balance the equation 

                                     Duration x Units/Time = Units

The following table illustrates how the variables in the above equation changes when you change one among them in each of the Activity duration types.

Duration Type
When You Change Duration, what
changes?
When you change units/time,
what changes?
When you change units, what
changes?
When you add a resource, what
changes?
Fixed Units/Time
Units
Duration
Duration
Duration
Fixed Duration and Units/Time
Units
Units
Units/Time
Units
Fixed Units
Units/Time
Duration
Duration
Duration
Fixed Duration and Units
Units/Time
Units
Units/Time
Units/Time
Table 1. Activity duration types
The duration type is set at the Project Details level for the Project, but can be modified per activity. Your organization’s project needs will help to determine which duration type to use. We’ll be discussing in the following section as of what situation forces you to choose a particular Duration type.
As a hint, if you are adding resources to activities and you do NOT want P6 to recalculate the existing resources units, duration and units/time, go to Edit, User Preferences from the Menu bar, select the Calculations tab and select the Preserve the Units, Duration and Units/Time for existing assignments radio button.

Example:-
Now let us consider a Case and work on it to get a better understanding on the Activity duration types.
Given Case :Consider a software company where a resource is assigned design work of a particular website. It is estimated that the design work would be completed within 5 working days of the resource. The particular resource has a regular shift duration of 8 hours /day.
Find what happens to values of the Original duration, budgeted units/time and Budgeted units when
i.                    Original duration changes to 10 days
ii.                  Budgeted units/time changes to 10hours/day
iii.                Budgeted units of  work changes to 20 hours                          In each of the activity duration types.
Findings:                     Original Duration =5 days ,
Budgeted units/time = 8h/d
From the formula we know Budgeted units = Original Duration  X Budgeted units/time = 8 x 5 = 40 hours
Type I :-Fixed Units / Time
Units/time for the resources remains fixed; Even when activity duration or budgeted units changes. Used when resources with productivity output per time period is fixed. Mostly used when Activity type is Resource Dependent. This option is selected if your organization is concerned with leveling resources and you assign resources specific hours per day on activities.
Original Duration = Budgeted Units / Budgeted Units/Time
Duration Type
When You Change Duration, what
changes?
When you change units/time,
what changes?
When you change units, what
changes?
Fixed Units/Time
Units
Duration
Duration
Table 1.1.1 Fixes Units / Time


Coming back to our case
            Where Original Duration =5 days ; Budgeted units/time = 8h/d And Budgeted units = 40 hours.
i.e. Original Duration = units / (units/time) รจ 5= 40 / 8
We were asked to analyze what would happen if
Changes made
(i) Original Duration Changes from 5 to 10 days
(ii) Units / time changes from 8 to 10
(iii) Units changes                     from 40 to 20
Values changed
Budgeted units
Budgeted units/time
Original Duration
Budgeted units
Original Duration
Budgeted units/time
80h
8h/d
4d
40h
2.5d
8h/d
Original duration
=>
(Units )/ (Units/time)
10=> 80/8
4 => 40/10
2.5 => 20/8
Table 1.1.2 Fixes Units / Time Workout



Type II: Fixed Duration & Units/Time
Activity duration and units / time remains fixed; even if remaining unit’s changes. Mostly used when Activity type is Task Dependent Activity. Organizations which have the project deadline fixed and is also concerned with leveling resources used this activity duration type. Organization may consider increasing number of resources to keep the resources leveled. Since this activity is Task dependant and activity duration type is fixed duration & Units/time there would be no layoff in duration time.

Original Duration = Budgeted Units / Budgeted Units/Time
Duration Type
When You Change Duration, what
changes?
When you change units/time,
what changes?
When you change units, what
changes?
Fixed Duration and Units/Time
Units
Units
Units/Time
Table 1.2.1 Fixed Duration & Units/Time


Given Original Duration =5 days ; Budgeted units/time = 8h/d And Budgeted units = 40 hours.
Changes made
(i) Original Duration Changes from 5 to 10 days
(ii) Units / time changes from 8 to 10
(iii) Units changes                     from 40 to 20
Values changed
Budgeted units
Budgeted units/time
Original Duration
Budgeted units
Original Duration
Budgeted units/time
80h
8h/d
5d
50h
5d
4h/d
Original duration
=>
(Units )/ (Units/time)
10=> 80/8
5 => 50/10
5 => 20/4*
Table 1.2.2 Fixed Duration & Units/Time Workout






Type III :-Fixed Units
This duration type is chosen if you want the activity units to be fixed even when duration or resource units per time changes. Total amount of Work is fixed. Used when Activity type is Resource Dependent Activities. Unlike previous Duration types increasing resources decreases the activity duration. Generally used when you have resource under contract basis and you have X units of work to get to be done from that particular resource.
Original Duration = Budgeted Units / Budgeted Units/Time
Duration Type
When You Change Duration, what
changes?
When you change units/time,
what changes?
When you change units, what
changes?
Fixed Units
Units/Time
Duration
Duration
Table 1.3.1 Fixed Units




            Given Original Duration =5 days ; Budgeted units/time = 8h/d And Budgeted units = 40 hours.
Changes made
(i) Original Duration Changes from 5 to 10 days
(ii) Units / time changes from 8 to 10
(iii) Units changes                     from 40 to 20
Values changed
Budgeted units
Budgeted units/time
Original Duration
Budgeted units
Original Duration
Budgeted units/time
40h
4h/d
4d
40h
2.5d
8h/d
Original duration
=>
(Units )/ (Units/time)
10=> 40/4
4 => 40/4
2.5 => 20/8
Table 1.3.2 Fixed Units Workout

Type IV :-Fixed Duration & Units
Activity duration and Units to remain constant even when the units/time changes. Mostly used when time period and the total amount of work are fixed. Used when Activity type is Task Dependent Activities. Rate at which a resource can work on the activity can be changed. You could use this if your organization is more concerned about coming in on the schedule date and within the costs (which are usually associated with the units)
Original Duration = Budgeted Units / Budgeted Units/Time
Duration Type
When You Change Duration, what
changes?
When you change units/time,
what changes?
When you change units, what
changes?
Fixed Duration and Units
Units/Time
Units
Units/Time
Table 1.4.1 Fixed Duration & Units
Given  Original Duration =5 days ; Budgeted units/time = 8h/d And Budgeted units = 40 hours.
Changes made
(i) Original Duration Changes from 5 to 10 days
(ii) Units / time changes from 8 to 10
(iii) Units changes                     from 40 to 20
Values changed
Budgeted units
Budgeted units/time
Original Duration
Budgeted units
Original Duration
Budgeted units/time
40h
4h/d
5
50
5d
4h/d
Original duration
=>
(Units )/ (Units/time)
10=> 40/4
5 => 50/5*
5 => 20/4
Table 1.4.2 Fixed Duration & Units Workout


Summary
Given Original Duration 5days; Budgeted Units 40hours; Budgeted Units/ time 8hours/day. The following table summarizes as of what happens to the variables in each of the activity duration types.
Duration
Type


Original Duration Changes from 5 to 10
Units / time changes from 8 to 10
Units changes from 40 to 20
Budgeted units
(Or. Val:- 40h)
Budgeted units/time(Or. Val:- 8h/d)
Original Duration
(Or. Val:- 5d)
Budgeted units
(Or. Val:- 40h)
Original Duration
(Or. Val:- 5d)
Budgeted units/time
(Or. Val:- 8h/d)
Fixed Units / Time
80h
8h/d
4d
40h
2.5d
8h/d
Fixed Duration & Units/Time
80h
8h/d
5d
50h
5d
4h/d*
Fixed Units
40h
4h/d
4d
40h
2.5d
8h/d
Fixed Duration & Units
40h
4h/d
5d
50h*
5d
4h/d
Table 2: Activity duration table chart
Or.Val -  Original Value          * - in certain cases original duration remains fixed and the other fixed variable is forced to changed.

Reference:-

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