Understanding Changing Assignment Units in Project

Often I am asked by Project users about assignment units and how can you explain the behaviour in MS Project, most often the questions are around why the % assigned units of a particular resource assigned to a task (an assignment) can change unexpectedly.

The situation can be explained through the following scenario using MS Project 2007:

  1. A Project Manager creates a task of 10 days, assigns a resource and sets the Units to 20% (15 hours of work with 1.5 hours planned per 7.5 hour day) using the task settings of Fixed Duration and Not Effort Driven.


  1. Now the Resource submits a timesheet that contains Monday = 1.5h, Tuesday = 0h, Wednesday = 1.5h.
  2. After the status update is accepted into the plan the resource Assignment Units has changed to 23% and a gap is shown in the Gantt chart bar.


This behaviour is expected. The cause is due to the missing day (Tuesday) of work which results in an additional 1.5h of work being spread across the remaining days of the task resulting in each remaining day now having 1.72 hours of work, or put another way a ‘peak’ assignment units of 23%.

This can lead to some confusion when looking at project schedules as if like many people your organisation assigns resources to work on such % allocations, typically through an approval process which dictates the "maximum" % allocation for any given resource.

The solution for the PM of course is to reduce the remaining work to return the peak units back to 20% ie in the above example subtract 1.5h work from the total. To see this do the following to correct the units in the above example:

  1. The Project Manager now edits the remaining work for the given task and reduces it by 1.5h, now the Units returns to 20%.



What’s new in Project 2010?

This behaviour has changed significantly in Microsoft Project 2010! In fact the behaviour now is closer to what you might expect; Microsoft has introduced a new field in addition to Assignment Units you now have Peak Units which shows exactly what you might guess from the name in the example above, in short you can see both the original “assigned units” of 20% and the actual “peak units” of 23% together.

See the following quote from Microsoft:

"In Project 2007, and previous versions, when this value differs from 100% we show it next to the resource name in the Gantt chart. For Project 2010 we’ve made some changes to the way that the Assignment Units field is calculated. Primarily, these changes were made in response to customer feedback about the way calculations were impacted when resources entered overtime work. For this release we’ve clarified the definition of the Peak field and the Assignment Units field which previously had some functional overlap but now fill more defined, separate, roles. As a result of these changes the Assignment Units field is no longer automatically modified to be greater or less than default value of 100%; as a consequence the field does not show up in the Gantt chart as often as it used to."

Source: Assignment Units in Project 2010

For more information on task types, assignments and such here is another good read on the topic;

Task Types: Don’t Get Frustrated!

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First real world 2010 issues..

Been very quiet on this blog the last couple of weeks, largely due to the fact that I’ve just kicked off my second PS2010 project (this one for one of the big mobile network management companies), while at the same time being in the thick of the first round of system testing for my first 2010 project!

I’ve got a handful of things I wanted to blog about but let’s start with some issues that I have come across, some of these I plan to log with MS, however none were really bad enough to cause any major concern.


1. Workspace Template Risks List ‘Exposure’ Unexpected Error

When you create a blank template site (not linked to a project) an ‘Unexpected Error’ will occur when you try to edit the field behind the default ‘Exposure’ field. This doesn’t happen when the site is linked to a project through the normal project creation.

Fortunately the standard calculation (Consequence * Likelihood) is all that I usually use anyway so this is a non-issue.


2. No Spaces Between Tasks when using PWA online editing

This one is causing some frustration, basically the Project Web App online editing does not support blank lines between tasks at all. Rather annoying as just about everyone I know uses spaces to make large projects more readable.


3. BCM Project Professional 2007 Crash when spaces exist between tasks

This one is related to #2 above, if you save a project template containing spaces between tasks (blank lines) and associate it with an Enterprise Project Type, then it seems when in BCM mode attempting to open a project created by that type will cause problems for Project 2007 client, but not 2010.

I didn’t fully test this one out to find if there are any other factors, but after removing the blank lines from my templates both this and #2 were fixed.


5. Project Client version restriction ignores CU build numbers

This one is more of an annoyance, it seems that the new feature in server settings to restrict the version number of connecting Project Pro clients only recognises major build numbers, ie Service Packs. Meaning that trying to force all 2007 clients in BCM mode to run at least Feb2010 CU will be just as troublesome as it always was.


5. Project Template used by EPT with Budget Resources assigned causes failure to create project

This is probably the worst issue I have found, I like the Budget Cost feature but it doesn’t seem to be the most widely used feature if an issue like this can slip through testing. I’m probably going to log this one with MS, but for this particular customer we simply modified our procedures to work around it. Here is my full issue description:


Attempting to save an Enterprise Template and associate it with an Enterprise Project Type when the template includes Budget Resources assigned to the Project Summary Task causes a failure in the project creation queue job(s).


Project Server 2010 RTM

Project Professional 2007 or 2010

Reproduction Steps:

  1. Create a new blank project in Project Professional
  2. From Tools – Options menu select ‘Show Project Summary Task’ (or equiv ribbon in 2010)
  3. Select Resource Sheet view, then add a single Cost Resource named ‘Test’
  4. Double click the resource to edit properties, and select ‘Budget’ to set the resource as a Budget Cost resource
  5. Assign the Test resource to the Project Summary Task
  6. Save As  to save as an Enterprise Template named ‘Test Template’
  7. Open PWA, go to Server Settings – Enterprise Project Types
  8. Create a new Project Type as follows;
    1. Name: Test type
    2. Workflow: No Workflow
    3. New Project Page: Proposal Details (or anything else)
    4. Project Plan Template:  Test Template
    5. All other values default
  9. Select Project Centre, New Project – “Test type”
  10. Enter the details and Save


Queue job fails with the following error:



Table Assignment

Row: ASSN_UID=’18a3ec42-a1ad-415b-9e38-5b822f38750e’ PROJ_UID=’09c32ca4-5d86-4b0b-91f0-21e8abe97e3c’

Error TaskNotFound (7021) – column



GeneralQueueJobFailed (26000) – ProjectCreate.ProjectAddToMessage. Details: id=’26000′ name=’GeneralQueueJobFailed’ uid=’b6640d9d-36ab-496d-b210-7b765ea852ea’ JobUID=’abf46cad-10b1-4e7c-94b8-6beeb76b30c5′ ComputerName=’AU-GLB-MSP04′ GroupType=’ProjectCreate’ MessageType=’ProjectAddToMessage’ MessageId=’1′ Stage=”. For more details, check the ULS logs on machine AU-GLB-MSP04 for entries with JobUID abf46cad-10b1-4e7c-94b8-6beeb76b30c5.

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