Critical Path through multiple Projects

[BigFish311]

I am currently using MS Project 2000 and having issues calculating the
critical path through 3 different schedules. When I open up the total slack
column and starting tracing it manually backward I see a change in the total
slack value when the link crosses from one project to another. On a couple
of the links that I see the change in slack they have around 30 days of lag
on them. First off, that big chunk of lag is not my decision to use, but
when that amount of lag goes over a holiday break should that change the
number in the slack field because I sometimes can count the holidays and that
same amount is the change in slack? These changes in slack are sometimes
negative and I have no deadlines, must start, or must finish constraints set.
I appreciate any help on this issue. Thanks.

 

[JulieS]

Hi BigFish311,

When consolidating multiple project files, Project by default, only
calculates the critical path across the longest path. So if you have
multiple, overlapping schedules, you may see critical path in a short
duration project disappear all together. Go to Tools > Options, Calculation
tab and select "Calculate multiple critical paths." Project will then
calculate critical path (including Total Slack) for each project.

I hope this helps. Let us know how you get along.

Julie

 

[John]

I am currently using MS Project 2000 and having issues calculating the
critical path through 3 different schedules. When I open up the total slack
column and starting tracing it manually backward I see a change in the total
slack value when the link crosses from one project to another. On a couple
of the links that I see the change in slack they have around 30 days of lag
on them. First off, that big chunk of lag is not my decision to use, but
when that amount of lag goes over a holiday break should that change the
number in the slack field because I sometimes can count the holidays and that
same amount is the change in slack? These changes in slack are sometimes
negative and I have no deadlines, must start, or must finish constraints set.
I appreciate any help on this issue. Thanks.

BigFish311,
First of all, a Project schedule doesn't require a constraint to have
slack. If there are no other constraints, Total Slack will be calculated
based on the finish date of the last task. However if you are seeing
negative values in the Total Slack field, then somewhere in your
schedule, one or more tasks is "holding" things up. Take a look at the
Constraint Type field. A typical constraint that can cause negative
slack is a constraint of "finish-no-later-than". For other things that
can cause one or more tasks to be "fixed", go to our MVP website at:
http://www.mvps.org/project/faqs.htm
and take a look at FAQ 50.

To answer your other question, yes, a lag on a task may affect the total
slack. Inserting a lag is like adding a fixed amount to the duration of
a task. Lag is in working days so the amount by which Total Slack is
affected could very well be impacted if the lag is inserted over
non-working time (e.g. weekend, or holiday period).

Hope this helps.
John
Project MVP

 

[BigFish311]

Thankyou both for replying but my issue is that say this one activity has 0
slack, no constraints, and only 1 predecessor. So I trace it backwards and
the predecessor has a -8 days of slack on it. The predecessor is in a
different project and has no constraint on it. The link between these is FF
with a 40 day lag. Where does that
-8 come from? The funny thing I found though is that within that 40 day lag
it goes over Christmas break which has 8 holidays set within that time. Now
is this a coincidence that the critical path went from 0 to -8 or is it
because the lag went over the holiday. I have been tracing the critical path
backwards from the very end (THE FINAL MILESTONE HAS 0 Slack) and found a few
of these incidents when crossing from file to file. I know this problem
would be easy to show vs trying to explain in text.

 

[John]

Thankyou both for replying but my issue is that say this one activity has 0
slack, no constraints, and only 1 predecessor. So I trace it backwards and
the predecessor has a -8 days of slack on it. The predecessor is in a
different project and has no constraint on it. The link between these is FF
with a 40 day lag. Where does that
-8 come from? The funny thing I found though is that within that 40 day lag
it goes over Christmas break which has 8 holidays set within that time. Now
is this a coincidence that the critical path went from 0 to -8 or is it
because the lag went over the holiday. I have been tracing the critical path
backwards from the very end (THE FINAL MILESTONE HAS 0 Slack) and found a few
of these incidents when crossing from file to file. I know this problem
would be easy to show vs trying to explain in text.

BigFIsh311,
It's been a long time since I worked with critical path in a
consolidated master (way back to Project 4.x) but there is [generally]
always a reason for Project showing what it does. I agree it would be
much better to actually see your file and play with it a bit. I would be
willing to do that if you don't mind sending it via e-mail although I
may not be able to look at it for a several hours. If you want to send
it, here is my address.

If you decide to send it, please detail the area of question.

John
jensenj6atatcomcastdotdotnet
remove obvious redundancies