Planning for unplanned assignments (maintenance projects)

T

Tvrtko Begovic

What is the best way to plan resource assignments for tasks that occur
sporadically and in irregular intervals?
For instance, we have two types of projects - development projects and
maintenance projects.

Development projects are easy to plan because they have estimated effort,
you know the start date and they are more or less linear i.e. they are being
worked on from beginning to end continuously. It is pretty easy to plan
resource utilization for them.

On the other hand, maintenance projects are different - you can only guess
how much effort would be spent on them in advance because you don't know
your customer future wishes regarding change request and problems with bugs
(mostly it is about change requests and new functionalities). You don't know
start date (they can ring any time any day and demand your action) and the
worst, they are not continuous - you can spend two days on one issue, then
do nothing for five days, then spend another day working on another request
and so on. If you assign some of the resources that work on development
projects to these maintenance projects, what is the best way to plan their
assignments and utilization?
I played a little with various options but I am still not sure what would be
the best way:

1. If I don't share resources between projects (no resource pool, every mpp
file has its own resources), then I can assign less available units of work
to those resources that work on maintenance projects so they would be less
available to development projects. For instance, if Pete works on my
development projects and also on some maintenance projects, and from recent
experience I presume that he spends 20% of his time on maintenance projects,
I would assign him 80% availability on development projects and 20%
availability in maintenance projects.

The problem is here that if number of simultaneous projects goes up,
manually adjusting resources in separate projects can be very painful. So, I
WANT TO use resource pool. However, if I share resources, availability is
also shared, so if I set Pete to have 80% availability, then it seems he is
generally 80% available and that is not what I wanted.

2. The other option I tried is to play with calendar. I can set Pete's
working time to be 80% of normal working time and presume that he would work
the rest on maintenance. The problem is here that I don't know how to plan
and track maintenance projects. If I use them with same resource pool, I
would end again with Pete having only 80% availability, this time not
because of available units but because of less working time per day.

3. The third option is using recurring tasks. They seem to me like the best
option - I can plan with the best possible accuracy (although not perfectly
but such is the nature of maintenance projects), I can use resource pool and
I don't have to adjust calendar. So, if I estimate that Pete's effort on
maintenance projects is average 20% per week, I can assign him recurring
task that occurs every week and has duration of one day (20%). If he spends
more time on that task, he would enter the correct data in his timesheet and
it would reflect actual work. Am I missing something or that's it?

I also read something about administrative projects. You can enter tasks
like vacation and sick leave and record actual time against them without
prior knowing how much they would take. BUT...as Dave pointed out in one
post, in order for those tasks to be propertly included in scheduling and
leveling, they must also be entered in calendar as non-working time. But
obviously my maintenance projects don't fall into this category, because
they have to be planned and affect the schedule of other projects.

Thanks for any enlightenment on that subject

Regards,
Tvrtko
 

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