To cost load a project using Primavera P6, you need to create and assign resources. When assigning resources, there are several settings that you should consider. Specifically, these resource assignment settings will determine what happens when you assign multiple resources to a single activity. If you have multiple people working on one activity, the activity’s units and durations may decrease. However, this is not always the case. It’s a good idea to examine the resource calculation settings for each project to ensure they’re working as needed. Along with these resource settings, you can also configure an activity’s Duration Type. The Duration Type will determine what values stay fixed and what values change as you assign additional resources.

In this article, we will take a look at how the resource assignment settings work in Primavera P6. We will also look at each of the different Duration Types, and how they can affect your activities. The following examples are from Primavera P6 Professional 20. However, you can find these same tools in all versions of P6.

Adjusting the Resource Assignment Settings

To view or adjust the current resource assignment settings, select Edit > User Preferences.

The settings you choose here will only affect you as a user. Other users in your database may use the program with different settings, as needed.

From the User Preferences window, select the Calculations tab. Here, under Resource Assignments, you’ll have two options available. These options will determine what happens when you add or remove multiple resource assignments to a single activity. You can choose to either:

• Preserve the Units, Duration, and Units/Time for existing assignments, or  
• Recalculate the Units, Duration and Units/Time for existing assignments based on the activity Duration Type

By default, this setting will be set to preserve these values. Let’s take a look at how each of these resource assignment settings work, starting with the default.

Preserve the Units, Duration, and Units/Time for existing assignments

The default resource assignment setting will preserve activity values, even as you add additional resources. Instead of minimizing the units and durations needed, these values will stay the same. The same is true for the units/time of the assigned resources – they’ll work full time on the task, even if multiple resources are working.

In this example, I have just begun assigning resources to activities. My activity Install Underground Footings has a duration of 5 days and will require several resources. I’ll start by assigning my first resource to the activity. To do this, select the Add Resources button from the Resources tab in the Details section.

I’ll select my resource, Bill Andreson, and press Assign.

Bill Anderson works 8 hours per day by default, and this activity has 5 days of duration. Assigning him to this activity has given him a total of 40 units, or hours. By default, the program assumes that he will be working full time for the entirety of the activity.

Now, let’s see what happens when I assign another resource to the same activity. Once again, I’ll select Add Resources. This time, I’ll assign Robert Smith to the activity.

Robert Smith also works 8 hours/day, and he was also assigned to work all 5 days of the activity’s duration. Altogether, he also received a total of 40 units for the activity – bringing the activity’s total units to 80.

This is what will happen when you choose to Preserve the units, duration and units/time for existing assignments. As you add additional resources to the activity, they’ll continue to be assigned to work full time. Instead of minimizing the duration for the activity, or the units/time for the resources, these values will stay fixed. You’re simply adding more resources, without taking away the amount of time needed for the activity.

With this setting, we are assuming that nothing will change with the activity as we add more resources. Instead, the units, duration, and units/time stay preserved.

Now, let’s take a look at what happens when you choose to have this data recalculated, instead. Once again, you can adjust this setting in the User Preferences window, under the Calculations tab.

Recalculate the data for existing assignments based on the activity Duration type

The other resource assignment option is Recalculate the data for existing assignments based on the activity Duration type. This option will recalculate data for the activity as you add additional resources. Specifically, this option will look at the activity’s assigned Duration Type to determine which data to recalculate. You can view and edit an activity’s Duration Type using the General tab of the Activity Details.

There are four options available for Duration Type:

• Fixed Duration & Units,
• Fixed Duration and Units/Time,
• Fixed Units, and
• Fixed Units/Time.

When you add additional resources to an activity, the activity data will recalculate. The Duration Type allows us to choose which data to stay fixed – or unchanged – in this process. Any non-fixed data will recalculate as you make additional resource assignments.

Let’s take a look at how the Recalculate setting works with each of these different Duration Types.

Fixed Duration & Units

Fixed Duration & Units will keep the activity’s duration and units fixed as you assign additional resources. This duration type is useful when you know both the duration of the activity and the amount of resources required. This is the recommended duration type for time and budget constrained projects.

To see the effect of this Duration Type, I’ll assign another resource to the activity. Returning to the Resources tab, I’ll assign Robert Smith once again.

With the Duration and Units fixed, the activity’s duration has remained at 5 days and the overall units at 40 hours. However, with another resource assigned these units are now split between both resources. Each resource now only needs to work a total of 20 hours to complete this activity’s work. Because the duration has remained at 5 days, each resource now only needs to work 4h/d. With the Duration and Units fixed, the resource’s Units/Time have recalculated.

Fixed Duration and Units/Time

Fixed Duration and Units/Time will keep both the activity’s duration and the resource’s units/time fixed. You should use this duration type if your activity has a fixed time frame that won’t change, regardless of the number of resources. For Task Dependent activities, this duration type is most often used.

After assigning another resource, the activity’s duration has remained fixed at 5 days. The units/time for each resource has remained fixed at 8 h/d. With these two fields fixed, both resources are once again working 40 hours overall.

Here, we have the same result as if we had chosen to Preserve the Units, Duration, and Units/Time for existing assignments. As we add more resources, more units add to the activity – rather than minimizing the existing activity data.

Fixed Units

Fixed Units will keep the units assigned to the activity fixed, even as you add resources. This duration type is best used for activities where you know the amount of work needed. This type is most often used with Resource Dependent activities.

If you plan to use this Duration Type, make sure to adjust the activity units before assigning additional resources. By default, resources you assign will be set to work their default units/time on each day of the task’s duration. Currently, this activity shows 40 units overall – 8h/d multiplied by the 5 days of duration. Before assigning additional resources, I would want to change the activity’s units to the total amount required for completion. These units will then be split among the resources I assign to the task.

After assigning another resource, the activity units have remained fixed at 40. Now, however, those 40 units have split evenly between the two resources. The resources now only have to work 20 units, or hours, each. Each resource is still working 8h/d, which in turn decreases the activity’s duration from 5d to 3d. 

With the Units fixed, the assigned resources are now sharing the overall work. With both working full time, the activity can now be done in less time than originally expected.

Fixed Units/Time

Fixed Units/Time fixes the Units/Time for resources assigned to the activity. You should use this duration type when the resources are always working full time – regardless of duration or units. This type is also useful for activities that require multiple resources at once. For example, if an activity makes use of equipment that requires two resources to operate, you should use this duration type. Fixed Units/Time is most often used with Resource Dependent activities.

After assigning another resource to the activity, each resource is still working 8 hours/day. The activity units have stayed at 40 units overall. The two resources are now sharing those 40 units, working 20 units each. With both working full time, the activity’s duration has decreased to 3 days. With more hands on deck, we’re able to complete the activity faster than expected. 

Summary

In Primavera P6’s User Preferences, you can adjust how the program works with multiple resource assignments. Here, you can choose to either Preserve or Recalculate the Units, Duration, and Units/Time for existing assignments. By default, the program will keep this setting on Preserve the Units, Duration, and Units/Time for existing assignments. With this option, the activity and resource values will not change, even as you assign additional resources. I recommend using this option when first resource-loading the schedule. Many times, you’ll know the activity’s duration and the resources required – and you may not want these values to adjust.

The other option is to Recalculate the data for existing assignments based on the activity Duration type. This option will adjust activity and resource information as you assign additional resources. This option works with the activity’s Duration Type, which allows you to choose what data to stay fixed. Any non-fixed data, such as the Units, Units/Time, or Duration, will adjust as you assign additional resources. I recommend using this option only after you have assigned all required resources. This option is useful for performing what-if scenarios and dealing with issues – such as delays or overallocation. If you need to compress the schedule or clear overallocation, this tool can help you do just that.

As you continue working on the project, you can switch between these two Primavera P6 settings at any time. Even if you start assigning resources using the Preserve setting, you can always switch to the Recalculate setting as needed.

If you have any comments, questions or suggestions, please use the comment section on the bottom of this page. Don’t forget to subscribe to our blog to get more Primavera P6 tips & tricks directly in your inbox!

Lauren Hecker is the instructor for the Primavera P6 Professionals training courses. To see her next open enrollment course, please visit our calendar. To schedule an onsite or custom course, please contact us!