Overtime internal mechanisms

[Pinocchio]

What happens internally when I increase (or reduce) the field "Overtime" ?

I have a 50-hour task (duration 5days) assigned to a unique resources (125%)
I would like to set 10 hours as overtime to solve the over-allocation
warning.

Siuation 1:
Work: 50 hours
Overtime: 0
Unit: 125%
Timephased: 10 / 10 / 10 / 10 / 10

Situation 2: I set manually overtime to 10 hours
Work: 50 hours
Overtime: 10
Unit: 125%
Timephased: 12.5 / 12.5 / 12.5 / 12.5 / 0.0

Situation 3: I increase manually overtime to 11 hours
Work: 50 hours
Overtime: 11
Unit: 125%
Timephased: 12.82 / 12.82 / 12.82 / 11.53 / 0.0

Situation 4: I reduce manually overtime to 10 hours (similar to situation 2)
Work: 50 hours
Overtime: 10
Unit: 100%
Timephased: 10 / 10 / 10 / 10 / 10

Depending on my increasing or reducing the overtime allocation, MS Project
reacts differently.
Can anybody explain the logic behind this (still strange to me) behaviour?

Your MVB (Most Valuable Beginner)
Running Project 2002

 

[Gary L. Chefetz [MVP]]

Dear MVb:

Understanding overtime work

Overtime work is the portion of "Work," at a task or assignment level, that
is scheduled as overtime and whose cost is calculated using overtime rates.
Overtime work assignments create "schedule time" above and beyond the
standard work day. Unless you specify your own contours, the scheduling
engine distributes the overtime portion of the work following the same rules
it uses for distributing work.

To completely explain the behavior you're seeing, I should mention that
you're using a work day of 8 hours, that the task type you're working with
is fixed-duration and effort-driven. Changing these parameters affects these
behaviors as well. Effort-driven should generally be unchecked for fixed
duration tasks.

In this first example you simply applied the resource yielding the results
you show. Project Schedules the task for 10hrs each day over five days with
the over-allocation.

I have a 50-hour task (duration 5days) assigned to a unique resources
(125%)
I would like to set 10 hours as overtime to solve the over-allocation
warning.

Siuation 1:
Work: 50 hours
Overtime: 0
Unit: 125%
Timephased: 10 / 10 / 10 / 10 / 10

In the next example, you now alter the above state of the task by assigning
10 hours of work to overtime, however you don't change the units percentage
causing Project to reschedule the task to occur over a duration of four days
using the information you've provided: I want the resource to work at 125%
allocation during both the regular work period and during the overtime work
period. So, you end up squeezing 10 hours against regular work time and 2.5
hours of overtime work. What you wanted and needed to do here is set the
units back to 100% to end up with the same time phasing you in the example
above. You were almost there with this one.

Situation 2: I set manually overtime to 10 hours
Work: 50 hours
Overtime: 10
Unit: 125%
Timephased: 12.5 / 12.5 / 12.5 / 12.5 / 0.0

Ok, I can see where the below example gets confusing, but understanding the
above results explains the ones below as well, although this is what I like
to call a classic Project "calcamamie." The funky rounding at the end is a
slap on the wrist to remind you to think about using a time-phased view to
contour your own over-time assignments when you're not dealing with evenly
divisible overtime distributions and 100% resource units. After all, you
might get someone to stay four hours on Tuesday, but it's not likely on
Friday this time of year.

Situation 3: I increase manually overtime to 11 hours
Work: 50 hours
Overtime: 11
Unit: 125%
Timephased: 12.82 / 12.82 / 12.82 / 11.53 / 0.0

And you finally get to the state you want to be in with this arrangement.
The resource is scheduled to work 10 hours per day over five days with no
over-allocation.

 

[Pinocchio]

Dear Gary,
Thank you for your detailed answer. I think I understood the internal
behavior.
You are right that I should have mentioned that the task type was
fixed-duration.

I played again with my example under this new light and would like to
summarize:
a) when you increase overtime, MS Project keeps the unit (and moves work
forward).
b) when you decrease overtime, MS Project distributes work flat over the
duration and reduces unit accordingly.

The second behaviour seems more natural.
Indeed I didn't want to change the contour and only wanted to increase the
cost of the project (with overtime rate).

Thanks,
Your MVB (Most Valuable Beginner)