Primavera P6 Duration type is an important setting that determines how you want P6 to behave when an additional resource is added to an activity.
Duration type is an attribute of a P6 activity concerned with the managing of activity resource assignments. Primavera P6 Duration type is best understood through the prism of three terms:
- Duration – is the total number of working days for a respective activity.
- Units/Time – is the number of hours per day or daily effort planned for each resource on an activity.
- Units or work – is the total effort scheduled to be performed on an activity by all assigned resources.
Again, duration type becomes important when you assign multiple resources to an activity.
This article explains the differing duration types and their effect when an additional resource is assigned to an activity. Let’s look at the three attributes related to duration type. In Figure 1 below, we specify duration, units/time, and units.
Figure 1
Duration is the length of time or working days for the activity. The duration of this demonstration activity is 10-days. Each resource is assigned to this activity at a daily effort, which is 10-hours/day for this example.
Finally, the work or units of each resource is the duration multiplied by the units/time. This is 100-hours for each respective resource and 200-hours total for the two activity resource assignments.
For your duration type to influence your resource assignments you must set user preferences | calculations to recalculate the units, duration, and units/time for existing assignments based on the activity duration type. Duration type is set as a default but can be changed in the general tab of the activity details, Figure 2.
Figure 2
In P6 there are four duration type options to choose from:
- Fixed Duration and Units: P6 preserves activity duration and units and makes units/time the variable.
- Fixed Duration and Units/Time: P6 preserves the activity duration and units/time values. Units becomes the variable.
- Fixed Units: P6 preserves the Units or work value. Duration and Units/Time are the variables.
- Fixed Units/Time: P6 preserves the Units/Time value and makes duration and units the variables.
Now we demonstrate how the different duration types affect the way P6 manages multiple resource assignments on an activity. In our first example, Figure 3, using Fixed Duration and Units, we have assigned the resource Bob to activity A, a 10-day duration activity, at 10-hours/day.
Figure 3
The resulting budgeted labor units is 100-hours. Note the locks on budgeted labor units and original duration, Figure 3. Watch now what happens when we assign the additional Sue resource to activity A, Figure 4.
Figure 4
When Sue is included as an additional resource the labor units remains fixed at 100-hours and the activity duration stays at 10-days. Well, to keep the budgeted labor units value constant, P6 has divided the budgeted units/time between the two resources. They are now only working 5-hours per day each.
In our second example we fix duration and units/time, Figure 5, and assign resource Bob to activity B.
Figure 5
Again, Bob is assigned to a 10-day duration activity at 10-hours/day equating to a budgeted labor unit value of 100-hours. In this example duration and effort are fixed, and labor units made the variable. Let’s see what happens when labor resource Sue is added, Figure 6.
Figure 6
This time the budgeted labor units increases to 200-hours. Note the locks above original duration and budgeted units/time, Figure 6. Continuing we assign resource Bob to activity C with fixed Units duration type, Figure 7.
Figure 7
Again, we proceed and assign resource Sue to activity C, Figure 8.
Figure 8
This time the duration reduces to 5-days. P6 has a hierarchy when only one variable is fixed. P6 elects to modify duration first and the other non-fixed variable second. Now we fix effort, Figure 9, and assign our resource Bob to activity D.
Figure 9
When we add Sue the duration, again, reduces, Figure 10.
Figure 10
Now let’s see what happens when Units is fixed and we adjust duration, Figure 11.
Figure 11
When Units are fixed, and duration adjusted the budgeted units/time reduces to maintain the budgeted labor units’ value. Finally, let’s examine what happens when Units/Time is fixed, and duration modified, Figure 12.
Figure 12
Now budgeted units/time maintains at 10-hours/day, but budgeted labor units increases to 200-hours.
Summary
Primavera P6 duration type(s) allow you to control the three variables of activity assignment:
- Duration
- units/time
- units
Typically, in the planning stages of schedule development schedulers assign activities the fixed duration and units/time duration type. This makes units or work the variable. The work or budget will increase accordingly as additional resources are assigned to activities. Then once the budget is determined; it is approved.
After budget approval the schedule becomes both time constrained and budget constrained. (After a budget is approved it can be difficult to have additional budget changes authorized, so the schedule may become cost constrained). At this juncture it is best to assign activities the fixed duration and units duration type, i.e. time constrained and cost constrained type.