Resource Vs. Activity Calendar: How a Resource is Scheduled Using the Resource Usage Profile

Written on . By Tracy Mah

When we assign an calendar to an activity there is often some confusion on how the resource is scheduled to work. This is especially true when we have assigned a different calendar to the resource itself. By using the Resource Usage Profile, we can easily see how P6 distributes the work.

In a simple project scenario, we have assigned a 8 hour x 5 day workweek to a 20 day activity. This gives us Budgeted Units of 160 hours for each resource.

Original Duration x Units/Time = Budgeted Units 

20 Days x 8 hours/day = 160 units 

We have three resources assigned to the activity:

  • Resource 1: Works 8 hours x 5 days / week
  • Resource 2: Works 10 hours x 4 days / week
  • Resource 3: Is only available 4 hours x 3 days / week (Monday to Wednesday)

Global or Resource Calendars can be assigned to the resources in the Resource Window/Dictionary. The activity is a default Task Dependent Activity Type. This tells P6 that the resources will be scheduled according to the calendar assigned to the activity. It will not take the individual calendars assigned to the resources to schedule the work.

Let’s take a look at the Resource Usage Profile for each of the resources. You can access the profile on the Menu Bar > View > Show on Bottom > Resource Usage Profile.

Resource 1: 8h x 5d Workweek Calendar

As you can see for Resource 1, there are no issues and no overallocated units. This is because the Activity Calendar and the Resource Calendar assigned to the Resource are the same.

Resource 2:10 h x 4 d Workweek

As you can see, even though Resource 2 can work 10 hours Monday through Thursday P6 still assigns the resource to work only 8 hours per day. The red overallocated units also show that P6 expects Resource 2 to work on Friday, even though the resource is not available.

The black Limit line in the profile refers to the assigned Resource Calendar.

Resource 3 – 4 h x 3 d (Monday to Wednesday)

For Resource 3, you can see the scenario is even more evident. P6 still assigns the resource to work 8 hours Monday through Friday.

Let’s concentrate on Resource 3. What are our options to fix this?

Traditionally, it would be up to the Project Manager or Resource Manager to find alternative resources to work when a resource is overallocated.

Realistically, it isn’t possible for Resource 3 to work the Budgeted Units of 160 hours in the 20 day timespan. From the grah above, we see that they would only contribute 48 hours. The Project Manager would have to reduce the total Budgeted Units this resource would have to work during this period.

Another option would be to create three separate activities that have the same corresponding calendar as the respective resources.  As a result, we see that the Original Durations of the activities change from 20 days. For Resource 3, it changes to 40 days.

There are a lot of factors to think about when you assign resources to your activities. The Resource Usage Profile can help you make decisions on how calendar assignments and resource units are spread over the duration of an activity.