Critical path when summary tasks are linked?

[davekmd]

Folks, the 'classical' training (and pm s/w) I've previously used eons ago
would not allow linking (or assigning) summary level tasks. I've broken with
tradition and have created a rather large network of some 480 tasks using 5
WBS levels. I've done linking of summary tasks to other summary tasks.
(seems like a wonderful feature).

Initially when I filtered for Critical Tasks all I got was about 12 tasks
out of my 480. The 1st critical task shown was an overall summary task at
the highest WBS level, but no subtasks were shown underneath of it. This was
followed by a lower WBS level subtask, but this showed the subtasks.

So it was kind like this ...
3 mega summary task (no subtasks shown under this mega summary task)
3.7 summary sub task
3.7.1 subtask a
3.7.2 subtask b
3.7.3 subtask c
....etc.

Basically the subtasks under "3" weren't displayed. Now I did a search and
found that I probably needed to set the calculation option for multiple
critical paths. I have a bunch of critical paths now, so I suppose that's a
good thing.

My questions are ...
1. Is that right? I needed to enable multiple critical paths?

2. Is there any practical way to verify that what's shown are in fact the
tasks on multiple critical paths?

3. Is there an easy way to get a simple count of the critical path tasks?

4. Are multiple critical path schedules common / rare?

5. Generally speaking what gives rise to multiple critical paths (i.e., from
a modeling perspective what conditions generaly cause this?)

6. Are there any cautions I need to be aware of when linking summary tasks
to other summary tasks? (I have to be honest, this is pretty darn cool). I
can have 20, 30, 40 tasks at varying WBS levels under a high level summary
task for example "Step 1 office move". Then for the next mega summary level,
I can just make the task "Step 1 office move" the predecessor (FS) to the
summary "Step 2 office move". Slick. Nothing under Step 2 office moves
starts until everything in Step 1 finishes out.


Thanks much folks!

 

[Rod Gill]

Only link summary tasks when non of the tasks in the second group can start
until all tasks in the first group have finished. Then it's very valid in my
book because one link shows what has to happen instead of needing many
links. I much prefer simplicity.

 

[Mike Glen]

Hi Davekmd,

Welcome to this Microsoft Project newsgroup

This is a hot potato, as many who post here state that you should never link
summary tasks as they are not actual tasks where somebody does something.
They are also the first steps to getting circular references. These will
inevitably occur eventually when you are tempted to link real tasks within
one summary to others in another summary. Then come the temptation to
assign resources to the summaries. This, again, can cause chaos if you also
assign the same resources to the individual tasks, as the summary will be
duplicating the effort by trying to add to itself so to speak. Linking
summaries is thus best not done Having said that, I, personally, believe
this technique can be very valuable as you have pointed out. Provided you
have extreme discipline to never link anything outside the summaries and to
never assign resources to summaries, you should be successful - be aware of
the dangers though

With regard to ciriticl paths, be aware that if you assign resources and
then level, the indication of criticality could disappear as the leveling
(manual or automatic) will build in delays which mean that the float
calculations are affcted and the critical paths invariably disappear. I
tend to recommed that you clear levelling to see which tasks are critical,
apply more resources to them and then re-level to see the effect. You might
like to have a look at my series on Microsoft Project in the TechTrax ezine,
particularly #19 - Levelling for Results, at this site:
http://tinyurl.com/2xbhc or this:
http://pubs.logicalexpressions.com/Pub0009/LPMFrame.asp?CMD=ArticleSearch&AUTH=23
(Perhaps you'd care to rate the article before leaving the site,
Thanks.)

Multiple critical paths are more common than rare. You can see which tasks
are critical by applying the critical filter via Tools/Filtered for...
Alternatively you can insert the column for the Total Slack field where zero
slack means critical. Mutliple critical paths will typically occur when, for
example, the last task in one of your summaries is not linked to anything.

FAQs, companion products and other useful Project information can be seen at
this web address: http://www.mvps.org/project/

Hope this helps - please let us know how you get on

Mike Glen
MS Project MVP

 

[davekmd]

Mike, Ron,

Thanks much for the replies and welcome. Yes I applied the Critical filter
after enabling multiple critical paths and yes I got tons of critical tasks.
I believe you are correct as regards the source of critical paths in my
model. There are a number of 'dangling' tasks, last in the series of
subtasks. Yep, I wasn't thinking re: quickly verifying critical tasks. By
definition they'd have no slack.

I did not start out linking summaries. I had created a high level project
template that I wanted folks to follow, sent it out for people to add detail,
and low and behold one of the other consultants had created all sorts of
summary level linking and had all sorts of dangling, dead-ended tasks. Given
the time crunch and effort to remove the links and re-model, I left them in,
and .... started to use them myself when Project didn't object in the least!

Yes, I'm aware that leveling will alter my plan and have not (and will not)
'need' to use it as my tasks are of fixed durations.

As for the 'controversy', I can certainly see that. My 'classical' training
on building schedules was that only actual work tasks were ever linked and
assigned resources. I can see how circular references could arise.

I'll look over the articles and have the 'Mastering MS Project 2002' to
accomplish.

Thanks again, DaveK

 

[Mike Glen]

You're welcome, Dave

Mike Glen
MS Project MVP