Slack Time

[Bob Vardell]

Hello All!

I asked about slack time some "time" ago. I can go to view>slack time and
the times are shown in the new columns. What I am looking for is a way to
graphically show that in the Gantt Chart. Is there a way for the schedule to
be there, the critical path, and then a different color showing the slack in
between?

Thanks in advance!
Bob V.

 

[JulieS]

Hi Bob,

Take a look at the Detail Gantt view. Free Slack appears in the view as a
thin blue line following the Gantt bar.

You can change the Free slack to Total slack by changing the "Slack" bar
(Format>Bar styles) to draw to the Total Slack field instead of the Free
slack field and change the Text to Total Slack.

If you would like more detailed directions, please post back and I'll be
happy to explain.

Hope this helps. Let us know how you get along.

Julie

 

[Bob Vardell]

Julie,

Thanks! I got the color and name changed in the detail view so it is more
apparent. My question is this: Does simply changing the name of the bar in
the format area actually use the total slack time now? Also, does total
slack take into consideration the critical path and notify you of tasks that
are not complete when slack goes negative.

I know it seems like I am lost, maybe I am. I cannot find anywhere to get
this information but here. I cannot even find a class anywhere that teaches
such advanced functions. I wrote and taught a basic class to our company but
need to take it to the next level.

Thanks in Advance!
Bob V.

 

[JulieS]

Hi Bob,

You are welcome and thanks for the feedback. Don't be at all concerned
about being "lost" -- that is what the newsgroups are for
To clarify my directions about using total slack instead of the free slack
field in the Detail Gant:. Just changing the name of the bar won't cause
Project to use the Total Slack field instead of the Free Slack field. To
make the change:
In the Format>Bar Styles dialog box in the row where you changed the color
and the name, under the To column change the field from Free Slack to Total
Slack by clicking on Free Slack and selecting the Total slack field from the
drop down list.

Total Slack is what Project uses for the definition of critical path. Tasks
that have zero or less (negative) total slack are on the critical path.
Project does not "notify you of tasks that are not complete when slack goes
negative" unless you place a constraint on the task (for example a Finish No
Later Than) and the task is delayed where the constraint date cannot be met.
If you have the Planning Wizard enabled (Tools>Options, General Tab), when a
task is delayed and the constraint cannot be met, the Planning Wizard will
appear and alert you to the scheduling conflict.

For some great on-line information (in addition to this newsgroup) you
should take a look at Mike Glen's (Project MVP) series of articles at:
http://pubs.logicalexpressions.com/Pub0009/LPMFrame.asp?CMD=ArticleSearch&AUTH=23

I hope this helps. Please post again if you need further help.

Julie

 

[Bob Vardell]

Julie,

You are a genius. Based on your explanation here I know why I am not
getting this......

When I go to format the bar, in the "To" drop down menu, there is no choice
for "slack" of any kind. When I manually type in the field name it tells me
that it does not exist.

What am I doing wrong?

Regards,
Bob V.

 

[Bob Vardell]

Oh, by the way, is it correct for me to assume that negative slack means that
I have "fallen off" the critical path?

 

[JulieS]

Hi Bob,

Thanks for the kind words but I am most definitely not a "genius" -- just
someone who has used Project for quite a while -- and has the grey hair to
show for it

Is there a choice in the drop down list for "To" for the field called "Total
Slack" -- not slack?

To your other question -- no, negative slack means that the task *is* on the
critical path and as the schedule is currently set, you are going to "miss
your dates" by the value of the negative slack. Tasks with positive total
slack are not on the critical path.

Hope this helps. Let us know how you get along.

Julie

 

[Bob Vardell]

Julie,

There is nothing in the drop down list that has the word slack in any form.

So, can I deduce that if the slack is zero on any red (critical) task in the
path than I am on schedule, if it is positive I am ahead of schedule, and if
it is negative I am behind schedule? Also, slack of any kind on a blue
(non-critical) task should not be paid attention to as it is superfluous
information.?.

Bob

 

[JulieS]

Hi Bob,

Okay. Let's just start from the top. When you choose Format>Bar Styles and
cannot see any fields containing the word "slack" (neither the field Free
Slack nor the field Total Slack -- they are arranged alphabetically in the
list) what view are you in? (Scroll the list until you see the fields
beginning with "t".)

What release of MS Project are you using?

When you say "on schedule", "ahead of schedule", and "behind schedule" I
assume you are looking for information comparing Baselines (your "planned
dates") and Actuals (dates and information you have supplied through
tracking.) To look at information comparing Baselines and Actuals, you may
like to see the Start Variance, and/or Finish Variance fields. These fields
specifically compare Baseline Start and Start fields (Start Variance) and
Baseline Finish and Finish fields (Finish Variance.)

By definition, critical tasks (red ones) have zero or less slack. I would
not go so far as to say that slack on a non-critical (blue) task is
superfluous. Slack is the amount of time the task the task can be delayed
before it becomes critical.

I hope this helps somewhat. Please post again with more questions.

Julie

 

[Bob Vardell]

Julie,

In order:

1. I was in the wrong field. I was in "Show For" not "To"....sorry, but
thanks so much for being patient.
2. I am using 2003 Professional.
3. I have a better understanding of the slack now.

Since you are so helpful, is there a way to get a view of the original
baseline, critical path, and the slack on the same Gantt?

Thanks!
Bob V.

 

[JulieS]

Hi Bob,

I'm happy to help and thanks for the feedback and sticking in there! Glad
you found the Total Slack field and good to know you have a better
understanding of slack.

To your question about original baseline, critical path, and slack on the
same Gantt. Yes, it can be done pretty easily.

I suggest making a new view so you can easily switch between a "regular
Gantt" and the formatted Gantt chart. To speed up making the new view, you
can copy and existing view and make the changes you need. To make a new view
by copying an existing view:

Choose View> More Views... in the menu to open the More Views dialog box.
Select the Gantt Chart View (or another if you have one that is closer) in
the list and click the Copy...button to open the View Definition dialog box.
Supply a new name for the view.
Select a table other than Entry if you have a preferred table.
Select a group or leave it to "No Group"
Select a filter or leave it to "All Tasks"
Click the Show in menu checkbox to enable if necessary.
Click the OK button to close the View Definition dialog box and return to
the More Views dialog box.

The newly created view should appear in the More Views dialog box and should
already be selected.
Click the Apply button to apply the view.
I like to run the Gantt Chart wizard to get most of the way there and then
tweak as needed.

To run the Gantt Chart Wizard:
Click the Gantt Chart Wizard in the Formatting toolbar.
Click Next> to proceed past the Welcome page
In the next step of the Wizard choose the option for Custom Gantt Chart and
click Next>
Choose "Yes" to show the difference between critical and non-critical tasks
and click Next>
Change the formatting, if desired, for critical tasks and click Next>
Change the formatting, if desired, for non-critical tasks and click Next>
Change the formatting, if desired, for Summary tasks and click Next>
Change the formatting, if desired, for milestone tasks and click Next>
Select Baseline and slack option button and click Next>
Make changes if you wish to the information displayed with the Gantt bars
and click Next>
I suggest leaving on link lines in the screen and click Next>
Click the Format It! button
Click the Exit Wizard button to close the Gantt Chart Wizard.

The Slack showing in the Gantt chart should be the Total slack and I think
that's everything you were wanting.

Please post again if you have any further questions and let us know how you
get along.

Regards,
Julie

 

[Steve House [Project MVP]]

Jumping in - negative slack doesn't mean you've "fallen off" the critical
path (not sure what you mean by that). Quite the contrary, a task that has
negative slack is firmly ON the critical path by definition. A task is
critical if its slack is less than or equal to zero, period. The critical
path is that set of tasks that drives the overall duration of the project -
it is the longest sequence of tasks in the project. A delay in a critical
task delays the project finish. A delay in a non-critical task does not
delay the project finish until it accumulates to the point that the task
becomes critical, ie, the task's slack time is eaten up. Negative slack
means there's a deadline or constraint of some sort that sets a mandatory
finish by date and the task is already scheduled so it misses that date.

These definitions make a bit more sense and are easier to visualize if you
make it a rule to always open the project with a "Start" milestone task and
end it with a "Finish" milestone task. All tasks in the project except
those two milestones MUST have both at least one predecessor and at least
one successor. If there's nothing required to happen before a given task,
its predecessor is the start milestone. If there's nothing else following a
task, its successor is the finish milestone. Links are based on the flow of
product and information through the project matrix and are NOT inserted
merely to create a desired time sequence - instead, they describe the
logical sequence in which the nature of the work itself drives the order in
which the tasks must be done, ie, I can't put on the roof until I've erected
the walls that hold it up. That means that in most real world prijects
there will be several, maybe many, parallel chains of tasks flowing from
start to finish. Sometimes the chains will converge into one sequence,
sometimes they will diverge out from one chain into several. OF all of
those chains, one of them will be the longest chain - that is, the critical
path. All of the tasks in that chain will have zero or negative slack. All
of the others will have at least some positive, non-zero slack, be it small
or large.

HTH