Can I constrain 2 tasks not to occur simultaneously?

[KellyB]

Is it possible to constrain 2 tasks such that they cannot occur
simultaneously? I don't care which task occurs first, I just want a warning
message or MSP to block me from allowing 2 tasks from being worked on at the
same time.

To make it even more difficult, it would be even better if I can still have
one task start before the other finishes, so long as one task occurs during a
delay (or split) in the other task.

Similarly, could I also constrain a task to occur within the start and
finish window of another task?

 

[Gerard Ducouret]

Hello Kelly

could I also constrain a task to occur within the start and
finish window of another task

If you want to schedule a lead time of 5 days between the 2 tasks, create a
Finish to Start link (FS) from the predecesor (row 10 for ex) to the
successor, such as : 10FS-5d
Another way : percentage : 10FS-50% (if the predecessor duration is 10 days)

Hope this helps,

Gérard Ducouret

 

[KellyB]

What I'd like to do is more tricky than that:

Task 2 should start any time AFTER task 1 STARTS, but Task 2 also needs to
end some time BEFORE Task 1 FINISHES.

 

[Steve House [MS Project MVP]]

I am really curious - what actual conditions could give rise to such a
requirement? Is it because a resource is required on both but can only be
on one at a time or is it something else? I ask because as you pose the
question there's no way for Project to handle it but perhaps you're not
asking the right questions <grin>. If you can give more details about the
exact circumstances and constraints we might be able to come up with an
approach that will work.

 

[JLB]

First you said you didn't want them to occur simultaneously. Now you say
that the second task *must* start and finish within the timeframe of the
first task. Simultaneous means "at the same time" and T2 is most definitely
running simultaneously with T1.

Task T1: give it a StartDate and Duration. (Actually, of course, you
shouldn't even be giving it a start date; that should be a function of the
end date and link with a predecessor task but we'll overlook that for the
purposes of this demonstration.)
Milestone M1: give it a SS link with T1 with a lag of 1d.
Milestone M2: give it a FF link with T1 with a lag of -1d.

Here's the tricky stuff:
Task T2:
(1) Click on the Start Date for M1 and press ctrl+c to copy the date.
(2) Click on the Start Date for T2, click on Edit | Paste Special |
PasteLink button | OK.
(3) Click on the Finish Date for M2 and press ctrl+c to copy the date.
(4) Click on the Finish Date for T2, click on Edit | Paste Special |
PasteLink button | OK.

If you change the T1 Start or T1 Finish then T2 will respond to those changes.

If you change the T1 Duration then T2 will respond to that change.

Now it's your turn: what are the real life tasks and why do they have to
behave this way?

 

[KellyB]

Thanks Steve and JLB.

Sorry about the confusion, but in my first post, I had asked about two
opposite scenarios: one being where the tasks could not occur simultaneous,
and the other where one task had to occur within the window (start & finish)
of another (as JLB pointed out, simultaneously).

My situation is this:
I'm planning both construction and maintenance activities of an electrical
system during a planned plant shutdown.

Firstly, my client (the plant) has outlined windows of opportunity for the
various sections of the plant. All work on their equipment must occur in
these windows, with different windows for various equipment. These windows
are somewhat flexible, so I didn't want to a SNET constraint and deadlines
for each task. If I manually move a task to a specific time (highly likely),
then my SNET constraint will be erased. Also, I want to be able to visually
see my constraints on the Gantt chart. As of now, I've set up the window of
opportunity as a task (with a different bar format) and used a SS link, so
that at least I can see which window of opportunity is applicable. I have to
manually verify the finish.

Secondly, as I mentioned, I'm planning both construction and maintenance
activities. Due to physical constraints and safety concerns, some tasks
cannot occur simultaneously. For example, I cannot plan electrical testing
of equipment while we're doing construction near that equipment. I can test
before, or I can test after, but not during.

I'll go back a take a look at JLB's suggestion. If you have further
suggestions, that would be appreciated.

Thanks,
KellyB

 

[KellyB]

JLB, see my reply to Steve for my real-world situation.

I've played around with your below suggestion, and I've found a solution to
one of my problems. I use a SS link to keep the start of Task2 within the
start of Task1, then I used your copy&paste-link method to link the finish of
Task1 to the Deadline of Task2. This way, I get a visual indication of if I
move a task outside my window of opportunity.

Great!

Now, do you have any suggestions for my other problem (preventing two tasks
from occuring simultaneously)?

Thanks,
KellyB

 

[JLB]

Not directly and you have to do a bit of a workaround which may/maynot be
applicable to you.

Basically, you need to have a dummy resource that you allocate 100% to tasks
that must not overlap. If you had, for example, t1, t2 and t3 which cannot
overlap and t4 and t5 which cannot overlap, you would create resource
Overlap1 and resource Overlap2. Assign Overlap1 to t1, t2 and t3; assign
Overlap2 to t4 and t5. By checking the View | Resource Usage display you
could see if those resources were overallocated (meaning they were scheduled
at the same time and this is indicative that the tasks which shouldn't
overlap are overlapping).

If you choose this approach, I would call them #Overlap1, #Overlap2, etc.,
so that sorting on the Resource Names will bring them to the top of the
display.

In addition, the View | Resource Usage display can be configured to show the
Start and Finish dates (and times, if you've selected that in the Tools |
Options | View-tab Date format).

This approach has a certain elegance, too, because you can build a bunch of
tasks underneath a single summary task and then have one more task
"Transition" that is an FS-link with the last task done and that only has the
#Overlap resource assigned to it. This would allow time to have the area
cleared before restoring power to it.

There is, btw, an "Overallocated" field on the View | Gantt display but that
is for a task (not a resource) and simply indicates that one (or more)
resources are overallocated on that specific task.

 

[KellyB]

Thanks.

So that I don't end up messing around with my work calculations, should I
set up the dummy resources as materials?

Not directly and you have to do a bit of a workaround which may/maynot be
applicable to you.

Basically, you need to have a dummy resource that you allocate 100% to tasks
that must not overlap. If you had, for example, t1, t2 and t3 which cannot
overlap and t4 and t5 which cannot overlap, you would create resource
Overlap1 and resource Overlap2. Assign Overlap1 to t1, t2 and t3; assign
Overlap2 to t4 and t5. By checking the View | Resource Usage display you
could see if those resources were overallocated (meaning they were scheduled
at the same time and this is indicative that the tasks which shouldn't
overlap are overlapping).

If you choose this approach, I would call them #Overlap1, #Overlap2, etc.,
so that sorting on the Resource Names will bring them to the top of the
display.

In addition, the View | Resource Usage display can be configured to show the
Start and Finish dates (and times, if you've selected that in the Tools |
Options | View-tab Date format).

This approach has a certain elegance, too, because you can build a bunch of
tasks underneath a single summary task and then have one more task
"Transition" that is an FS-link with the last task done and that only has the
#Overlap resource assigned to it. This would allow time to have the area
cleared before restoring power to it.

There is, btw, an "Overallocated" field on the View | Gantt display but that
is for a task (not a resource) and simply indicates that one (or more)
resources are overallocated on that specific task.

JLB, see my reply to Steve for my real-world situation.
[snip]

Now, do you have any suggestions for my other problem (preventing two tasks
from occuring simultaneously)?

Thanks,
KellyB

 

[JLB]

Ahhh ... simple cost tracking or Earned Value calcs? Hmmm. The machine I'm
on right now has P98 and doesn't know about materials so I can't say.

If you set the resource or material to have a value or rate of $0 then you
shouldn't have an impact on your total costs or on cost variances.

Your schedule variance could be a different matter. But since you're moving
lots of "task groups" (for lack of a better phrase) around you're probably
not concerned about schedule variances, you just want to make certain the
stuff gets done (and whether that's this shift or three shifts from now is
not a driving concern.)

That's the long answer.

Short answer: don't know; try both ways <grin>; report back.