Constraints with predecessors

[STEVO]

Hi all,

A high a query which is confusing me somewhat, grateful for any help.
I was always under the impression that for example, if you had 3 tasks
a,b,c and placed finish to start constraints on tasks a,b, & c and also
applied a "finish no later than" constraint on task c, that this would
mean tasks A&B would have to finish in time to honour tasks C's "Finish
no later than" constraint.

This was proved wrong, when i leveled a project recently, to find that
instead of getting a scheduling conflict message, tasks A&C had been
pushed back past tasks C's constraint date, but task C was still
scheduled to finish in time. This doesnt make sense to me as i thought
the whole idea of a predecessor was that it was a task that must
happend before the next???

If my knowledge is wrong, should I be placing "Finish no later than"
constraints on the summary task row, as opposee to the actual task
itself??

thanks
Steve

 

[Gary L. Chefetz [MVP]]

Stevo:

Setting a constraint on a task does not shield its predecessors from the
strange Voodo ways of the leveling algorithm in Project. The constraint
applies only to the task on which it is set. So Project, in this case, is
telling you that based on the leveling options you set, this is the best I
can do with this fine mess you made. Chances are you could get the leveling
engine to behave better by learning a bit more about it, and habitual
Project users generally find it liberating when they achieve a better
understanding of the scheduling algorithms. Leveling is a huge discussion in
itself. In this case, had you chose leveling settings that would have
prevented the tasks leading up to the constrained task from being
rescheduled, the system would not be able to resolve your overallocation.
Any way you look at it, it's an "impossible" set of facts for the system to
process. Chances are if it's impossible in Project's modeled world, it's
impossible in the real world as well. And, that is exactly the type of
output that makes the system valuable.

If you want to get into an in-depth discussion on best practices with the
use of constraints, I suggest you tune into our sister channel,
microsoft.public.project where several of my fellow MVPs are very sharing on
such topics. Although this topic affects Project Server, it's really more
appropriate for the project newsgroup as well.

 

[STEVO]

Hi Gary,

Thanks for your advice, I will endevour to find out more about the
levelling engine on the group you mention.

Thanks again for you kind assistance.

Regards
Steve