A comment on our blog on Resource Calendars asked whether the activity type of an activity using a resource calendar should be Resource Dependent? The answer is that it depends on what you want the scheduling software to do for you.
You are presented with six options when you proceed to describe the activity type of an activity in Primavera P6. These include: Finish Milestone, Level of Effort, Resource Dependent, Start Milestone, Task Dependent, and WBS Summary. The start and finish milestones are simply tasks with no duration that mark the beginning or end of a phase. A level of effort activity type is fixed between the start and finish of a series of activities, and will expand and contract according to the durations and relationships of those activities.
The WBS Summary activity type derives its duration from all the activities within a Work Breakdown Structure (WBS) element and becomes, in particular, handy as a high-level planning and estimating tool. Last but not least is the topic of this article; the Resource Dependent activity type – what is it and how should we use it?
This article describes the method and value of using a Resource Dependent activity type in a Primavera P6 Schedule.
Let’s start with a little context. The Resource Dependent activity derives its working days, and therefore its duration, based upon the calendars of resources assigned to it. Simply put, if the resource has some non-working period in their calendar, the activity will also be non-working during that time.
Using Resource Dependent Activities
The schedule for our example demonstration is in Figure 1.
The schedule is for a pipe repair and improvement project. The repairs are to fix leaks due to faulty pipe couplings. The improvement is to add a thrust block to prevent future coupling failures. The majority of activities have a Finish-to-Start relationship. However, the Insulate Piping activity has a Finish-to-Finish relationship with the strike forms activity, so that it could be performed in parallel with the concrete cure process. It is the Insulate Piping activity that we are most interested in.
Notice in the bottom right corner of figure 1 that the Pipe Insulator is scheduled to work four 8-hour days on the Insulate Piping activity. Eight hours a day is the maximum the Pipe Insulator is available to work. This agrees with the 8-hour per day work schedule for the Pipe Insulator on this activity, and, therefore there is no resource over-allocation.
This is displayed in the solely green resource usage profile bars of Figure 1 for the Pipe Insulator. Note that at this time no resource calendars have been assigned. The Insulate Piping activity duration is based upon the default project calendar, which is a standard five day 8-hour per day work schedule.
Our schedule appears to be all set for implementation. That is until the Pipe Insulator informed us he will be on vacation the week of August 10th. To account for this interruption in availability we create a personal calendar for the Pipe Insulator, Figure 2.
This is done in the resource sheet bottom pane Details tab. The vacation is defined as displayed in Figure 3, where August 10th through the 14th are Non-work days.
After defining this personal schedule for the Pipe Insulator we again view the resource usage profile of the Pipe Insulator, Figure 4.
Now we see that the Pipe Insulator is over allocated on Thursday and Friday, August 13th and 14th. This is because the Pipe Insulator is scheduled to be on vacation these days, as per the Pipe Insulator’s resource calendar. Note also that the activity type for Insulate Piping is still ‘Task Dependent’. Further, there is no change to the duration or start and finish of the Insulate Piping activity.
Now we change the activity type of the Insulate Piping activity from ‘Task Dependent’ to ‘Resource Dependent’, Figure 5.
When we do this and recalculate the schedule, we notice that the Insulate Piping activity has shifted two days forward thus removing the Pipe Insulator resource over-allocation. The activity is using the Pipe Insulator’s calendar to calculate it’s working and non-working days as seen in Figure 6.
So Primavera P6 has adjusted the start and finish dates of the Insulate Piping activity to accommodate the personal resource calendar of the Pipe Insulator that defines August 13th and 14th as non-work days. Note also that several activities that were previously critical are now non-critical. This is due to the delay of the Insulate Piping activity, as per the Pipe Insulator’s personal calendar.
Thus, in the Resource Dependent activity type the activity will base its duration, including start and finish dates, on the working and non-working days/periods of the assigned resource’s calendar. The task dependent activity type bases its duration on the working and non-working days of the activity calendar, which could be a global or project calendar. But where the Task Dependent activity type with assigned resource calendar will only display over-allocations in the resource usage profile, the Resource Dependent activity type will remove the resource over-allocation, accordingly.
Note that we did not assign a material resource to the Insulate Piping activity. If we had done so and not provided a similar personal calendar for the insulation material then the Insulate Piping activity would start earlier. The beginning of the activity would only display the material assignment, which does not make sense; you cannot install the insulation without the Pipe Insulator.
In order for Primavera P6 to correctly display the Insulate Piping activity on the Gantt chart you would have to assign the insulation material the same personal calendar as the Pipe Insulator, thus ensuring that both resources occur/function in parallel.
So task dependent activities base their duration on the working and non-working days of the activity calendar, whereas, Resource Dependent activities base their duration on the working and non-working days of the assigned resource’s calendar. So regardless of how many resources are assigned to a particular activity or task, the task dependent activity will only calculate durations using the assigned task calendar, hence the term Task Dependent. Resource Dependent activities adjust to resource calendars when resources are assigned.
If you are fine with Primavera P6 adjusting the resource over-allocation for you then use Resource Dependent activity type. But if all you want is to view the resource over-allocation in the resource usage profile, then stick with the task dependent activity type even when you assign a personal calendar to an activity. Be careful when you use the Resource Dependent activity type, as you will have to account for the calendars of all assigned resources.