allocating resources messes up work spread

[Steve Scott]

I have several 3 month fixed duration task and have spread the work out
across the months using the task usage view. In some cases the work does not
start until the 2nd month. When I assign a resource to the task, it pulls
the work in the 2nd month forward to the 1st month which was showing zero
work.

Is the way around this to always ensure fixed duration tasks have some work
at the beginning of the period ie I should have set the start date to
conincide with month 2?

 

[Steve House [Project MVP]]

A task's duration is the time between the instant when work is first
performed on the task and when it is finished. So it is a contradiction in
terms to say a task has a 3 month fixed duration on the one hand but the
work doesn't begin on it until the 2nd month. You may be able to do a task
starting any time after 1 January and need to have it finished no later than
1 April but that does NOT mean it's a 3 month fixed duration task. If work
starts 1 February and finishes 01 April that's a 2 month duration task and
the fact that it COULD have begun as early as January doesn't mean anything
or make its duration longer. It's the period of time the resource is
actively involved in observable physical actions that counts.

I have a real problem with the way fixed duration tasks are often used.
Somethings are fixed duration - a 24 hour burn-in test takes 24 hours, no
more and no less, for example, while paint takes X hours to dry no matter
how many resources you have watching it - but since a task duration models
the time period during during which works takes place on it and time that
tasks will require to get 'em done depends on how many resources you put on
and how hard they work on 'em, fixed duration tasks are really quite rare
birds. Many people tend to think the duration of a task is the time you
will allow for it in the schedule but that's not really the case - it's
supposed to be an estimate of the time over which work will actually take
place once it starts, whenever that may be.