MS Project resource assignment issue when assignment is 100% and Max Units is greater than 100%

Question

I wonder if MS Project 2013 is inconsistent in a particular case.

Suppose you have a task with a duration of 1.5 days. No resource is yet assigned. Now starting in that situation I will do three different "first assignments" allowing to compare the results (see below Task Usage before any assignment).

Task Type is Fixed Units and it is NOT effort driven.

First I create a resource, which has a maximum unit of 400%, my resource is called Employees (see below).

Now I propose to do three cases (always starting form the task in the starting situation as shown above):

1. I assign the resource Employees with an assignment % of 50%
2. I assign the resource Employees with an assignment % of 400%
3. I assign the resource Employees with an assignment % of 100%

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1. Assignment of Employees with assignment 50%

I receive following result:

This is exactly what I expected. A resource at 50% during 1.5 days corresponds to 6 hrs work.

2. Assignment of Employees with assignment 400%

I receive following result:

Again this is what I expected. A resource at 400% during 1.5 days corresponds to 48 hrs.

3. Assignment of Employees with assignment 100%

I receive following result:

Now this is NOT what I expected. Why does MS Project changes the duration of the task from 1.5 days to 6 days. It also gives the same calculation of work as in the case 2. It looks like when you enter 100% the system looks at the max. units of the resource and uses it to calculate the work and then levels it over a new duration taking into account the 100% assignment. But I am pretty convinced it should not take into account the resource's max. units.

I was expecting to have a resource at 100% during 1.5 days giving a work of 12hrs.

Is there a logic explanation? I cannot find one. I would appreciate if someone can explain this, or agrees with me that this looks like a bug.

Answer 1

I did not really had an answer to my problem and therefore I have further tested it. With the information I had from Jan De Messemaeker who kind of agreed that there was an issue but in version 2010, I tried the following:

I created four separate projects (so my tests are done in parallel, to make sure they do not influence each other). And in each project I just created a task with a duration of 1.5 days and added a resource called Employees with a Maximum unit of 400%. For assigning the resource (with units=100%) to the task I used 4 different methods. Every project used another method, but every time I entered 100% for the units to assign:

• The file "Assignment via Resource Window" used the Assign Resource button on the Resource tab. The result seems OK to me. The duration stays on 1.5 days and the work has been calculated at 12hrs.
• The file "Assignment via Resource Names Columns" used the possibility to check the resource in the cell in the Resource Name column that you find in the view Gantt Chart. Here I did not enter 100% as it is just a check box, but the default value is 100%. The result is again OK to me. It has the same result as above.
• The file "Assignment via Task Information Screen" used the possibility to double click on the task and to enter the resource via the resource tab. Amazingly I have entered 100% in the Units column but still it has changed it into 400%. The results for me are wrong and different from previous results. It has kept the 1.5 days duration but work has been calculated at 48hrs. I can assure you that I entered 100% but for any reason I cannot explain it has replaced this by 400%.
• The file "Assignment via Task Details Split Screen" used the Detail information screen you obtain when clicking on the button "Display Detail Screen" on the Task tab (I used Resources and Predecessor detail screen). Here I obtain again a different result. It has changed the task duration to 6 days and has calculated work at 48 hrs. The Employees resource has units of 100%, as I entered it.

See below print screens

For me, whatever the reason, which I cannot explain, there is a consistency problem. At least in my version of MS Project 2013. I have used the standard options. The only thing I changed is the option to have the new tasks as Auto Scheduled for all new projects (which when just installed is by default manually scheduled).

I am interested to know if anybody else has the same problem.

Answer 2

Dag Jan,

Thank you for trying replicating my problem.

As you do not have the same results as I have on MS Project 2013, I guess we should have either different versions or option settings.

However, it kind of scares me that you obtained different results between MS Project 2010 and 2013. I never heard about changes at that level between the two versions.

Kind Regards / Groeten

Answer 3

Dag Luc,

I started doing some tests and what I saw was very confusing.

Each time I tried assigning the resource in 4 different ways:

• Through View, Details
• Through Task Information, Resources Pad
• Writing directly into the Resource names column
• Using the Assign resources box

When doing all this in 2010, Dutch version, I reproduced your (wrong) result through the first 2 methods but the right reqsult (12 hours of Work) through the final two methods

Then I swithched to 2013, English version, and guess what? ALL FOUR methods provided the right rult - 12 hours of work!

So sorry, I cannot reproduce the error in your version :-(

Groeten,

Answer 4

Hi Trevor,

I assure you that I did exactly what I wrote. That is why I am confused.

This morning I just tried again from scratch (a new project) executing the third case only (meaning I have not made any changes to an existing situation as you suggested). And the result is exactly the same, which I cannot explain.

Please try it out.

For you convenience I have included MS Project version number: Project 2013 (15.0.4771.1000) MSO (15.0.4771.1001) 32 bit

Answer 5

First of all, there is no way this is a bug, and in any case it is far too early in your investigation to jump to that conclusion. This is how it works.

Where you say "It looks like when you..." the first part of your hypothesis is wrong because MSP does not use max units to calculate work, and you are correct where you are sure that it should not. Also, MSP definitely does not "level" anything unless/until you tell it to. And also, far from being inconsistent MSP is relentlessly consistent.

Although you say that you start with the same starting point in each case, it is clear that you did not start with a duration of 1.5 days and no resource assignment and no work in case 3. If you had, then after assigning the resource at 100% to the 1.5 day task the work would have been 12 hours as you expect. What you did was change the resource assignment in case 2 from 400% to 100%. How MSP responds to such a change depends on the task type and effort driven settings for the task in task information, advanced. Your current settings are task type = fixed units and effort driven = off, same as mine, and that's the default for MSP2010, and I got the same result as you did.

MSP has three task types and effort driven can be on or off for two of them and on only for one of them, making 5 possible responses to a change in duration or a change in work or a change in resource units.

When you check this out, try making max units 50000% and see that max units has nothing to do with it.

Max units is just a set point to decide if a resource is over-allocated.

And by the way, it is better to create 4 separate employees, each with max units = 100% and assign them all to the task.

The reason is that later when you are leveling you will have more control, more options etc.

Any help? Mark as answer?