There are 3 types of Resources in P6: Labor, Non labor and Material.
Resource units are assigned as hours/day. You can also specify the total budgeted units for the task and the hours/day will be auto computed from the total duration.
Labor includes manpower; Non labor refers to machinery/equipment; Material means the consumables, e.g. Tiles, Blocks, Paint, etc. The field for unit of measure is enabled only when Material resource type is selected.
When adding a Resource (Enterprise >> Resource), while specifying the defaults values, the application will also ask for the Max Units/Time. This term denotes the maximum availability of the resource, i.e. how many hours of a particular resource are at your disposal in a single day. Suppose you have a resource named Carpenter. The default units/time of this resource are 8hr/day. Meaning this resource will work for 8 hours in a day. If you have 5 individuals working as Carpenter in your manpower team, that means in one day you can have a maximum of 5 x 8 = 40 hours available. Therefore, in this case, for Carpenter resource, the Max Units/Time will be 40 hr/day.
The Max Units/Time specification allows you to analyze the distribution/requirement of resources per unit of time in your schedule and compare with the maximum availability in your team. Depending on the outcome, you may have to mobilize more resources to overcome any shortcoming or you may have to spread out the tasks in order to lower the total daily requirement within availability. This is called Resource Leveling.
Resource Leveling is not always enough to solve the over allocation problem. Consider a project with a single activity of 10 days. This activity needs a resource to perform 1,000 hours. That is, 100 hours a day (linearly, for simplicity’s sake). If the max units/time (team size) for this resource are only 80 hours/day then no matter what you do by way of leveling, over allocation of 20 hours/day would always exist … UNLESS you;
1. Either increase the activity’s duration to 1,000 / 80 = 12.5 (~13) days, or
2. Increase team size to have 100 hours available each day.
Consider this example;
The above image shows budgeted resource units for relevant activities. Over allocations for this resource (R1) are shown in red. The picture below shows time distribution of the same units.
Click Tools > Level Resources
Multiple options can be chosen here. Leveling priorities are predetermined at activity level and/or project level. Lower the priority number, higher is the priority level, i.e. higher priority activities are leveled first.
After leveling, this is the change observed:
Apart from the ‘leveling’ change in histograms, also notice the duration expansion. To understand the changes, let us look at some details.
Resource R1 has a Max Units/Time value of 30. This resource is assigned to some activities, A1030 and A1040 among those. Let’s see the budgeted units of R1 for both these activities.
A1030 Budgeted Units of R1 = 1,000 over 10 (working) days
A1040 Budgeted Units of R1 = 240 over 10 (working) days
Looking at the same info distributed time wise:
The above are the as planned resource allocations. Because of the overlap between A1030 and A1040, as you can see in the deep blue bar in the time scale, the daily requirement of R1 is 124 hours whereas only a maximum of 30 hours are available per day.
Once we execute the resource leveling command, this is how the redistribution happens, based on leveling priority.
A1040 (having low leveling priority, not shown here) is rescheduled to commence after A1030, i.e. daily requirement is reduced from 124 for the overlapping duration to 100 without any overlap. However, over allocation of 70 (= 30 – 100) still exists. This is because while the project management software can reschedule activities with different leveling priorities competing for the same resource, it cannot change the budgeted resource requirements for tasks. Resource requirement for any activity is governed by the quantum of work involved and must be made available, either by increasing the duration of the activity, thereby lowering the daily resource requirement, or by increasing the daily availability of resources.
Similarly, status before and after leveling for activities A1070 and A1080 is shown below with post leveling over allocation reduced to only 2 from the pre-leveling values of 2 & 12: