All levelling does is shift tasks so as to delay some of the work. It never
adjusts anything else, only delays the start time of one or more tasks.
For simplicity let's say Joe works 8 hours a day. I assign him at 100% to
two different tasks currently scheduled for Monday, each of which will take
8 hours to complete. The means he is being asked to somehow magically do 16
man-hours of work during one single 8-hour time period, obviously something
impossible. When I do resource levelling, Project will take ONE of those
tasks and push it over to Tuesday instead of Monday. It'll make up its own
mind about which one it chooses to move, but if it's important to me for one
of them to be done before the other, I can set the priority on the task I
want done first to something higher than the priority on the other task.
In your case, you have 4 tasks, Tasks 1, 2, 3, and 4, all 4 hours each, and
the same resource is assigned on each at 80%. Perhaps they all start off
scheduled beginning Monday at 8am and show finishing at 12 noon. You didn't
say what the resource's Maximum Availability setting is but if it's between
80% and 100% it doesn't matter and for an individual it should never be more
than 100%. The instantaneous committment level at any point in time can
never exceeed the maximum availability. So as it stands before leveling,
Joe is working 8am to 12 noon on Monday but he's expected to be doing 4
things all at once, representing a required committment of 320% but he's
only capable of doing much less. When you level, the tasks will stagger out
so #1 remains on Mon 8am - 12noon, #2 is Mon 1pm-5pm, #3 is Tue 8am-12noon,
and #4 is Tue 1pm-5pm. On the other hand, if Joe's maximum availability is
LESS than 80%, Project balks and gives you an error message. Why? Even if
you just look at one of those tasks, you have scheduled Joe to work 80% when
his maximum is only 50%. There is no way leveling can SHIFT that task to
bring Joe's instantaneous commitment down to 50% - even staggering the
multiples leaves him at 80% during each task. The only thing that will
reduce it farther that is to EXTEND the tasks and make each of them take
longer (because a lower percentage means he's working slower on the task) as
well as move some of them. But that's simply not what levelling does, ever.
It has no way of knowing if that would even be an option because it doesn't
know what else might be going on that's not part of the project so it gives
you an "I can't fix it" message and kicks it back into your court for you to
handle by hand.
Don't make the mistake of thinking an assignment of "80%" means he works on
the project tasks 6 hours a day out of each 8 hour work day. Likewise a
maximum of 80% doesn't mean he's only availble to work on the project 6
hours out of each day. It does mean the equivalent of that, in a way, but
it's actually a little more subtle the way it works. An assignment of 80%
means that he is not working at full speed for some reason (not necessarily
slacking off, maybe he has other demands on his plate at the same time).
That means that during any arbitrary period of time, he can only convert 80%
of the time into man-hours of work. If we're looking at 1 week from the
task's start to finish, he'll produce 4 man-days of work, the amount of
output he COULD have done in 4 days if he had nothing else on his plate. If
he's assigned 80% to a 4-hour duration task, it mean he's going to be able
to generate a little over 3 man-hours worth of equivalent full-time output
over the course of working 4 hours. It does not mean he work's 3 hours - it
means he works 4 but only generates the output of 3 hours, 12 minutes
full-time work. If we say his maximum is 80%, that means we want to reserve
20% of his energy for other, unspecified stuff and we're gonna let him sort
it out for himself how he wants to prioritize his workday, meaning when we
assign him to an 8 hour long task, we're really only expecting him to
produce 6 man-hours of work, understanding that he is working on it
sandwiched in and amongst the other things he has to do.
HTH
--
Steve House [MVP]
MS Project Trainer & Consultant
Visit
http://www.mvps.org/project/faqs.htm for the FAQs
