Displaying Negative Slack

[Andrew K]

Can I make negative slack display in the Detail Gantt? I have a deadline 16
days earlier than the end-date milestone, so my total slack is a negative 16.
I've created a Total Slack bar in Format > Bar Styles, but the Total Slack
shows only for tasks with free slack. Choosing Negative Slack in the To list
doesn't produce anything.

 

[Dominic]

Andrew,

Provided there is a continuous sequence through your schedule - every task
with the exception of the first & last tasks having @ least 1 predecessor and
1 successor (using Milestones to "close" stages or phases and tasks tha thave
no obvious successors) AND that the last task in your schedule has a FNLT
constraint project will warn you when you are in danger of missing your
target date - the trigger being negative Total Slack. You can see the
negative total slack values in the "schedule" table displayed with the Gantt
chart.

As for displaying negative total slack in the Gantt chart do the following -
create a new bar style and elect to display it for "Critical" tasks - define
the shape, style and colour of the bar and the row it will be shown on - the
bar should display from "Late Finish" to Finish - this should then display
the Negative Slack.

In circumstances where you are forecast to overshoot your target completion
date the Negative Slack will tell you how much time you need to claw back,
don't be a hero and try to claw back more time than you need to - all you
have to do is achieve the target, finishing a few days earlier may involve
stress and increased costs.

For more hints and tips check the downloads and checklist sections of my
website - www.projectability.co.uk

Dominic

 

[Andrew K]

Dominic,
Thank you. A Negative Slack bar now displays nicely. You illuminated
Format Bar Styles for me.

A deadline on the last task acts like a FNLT constraint, yes?

Andrew

 

[Dominic]

A deadline will behave similar to a FNLT constraint - the subtle difference
is that if you have a FNLT constraint and you suffer a delay that results in
Neg Total Slack you get a clear and definite warning from the Planning Wizard
whereas with a deadline all you get is a RED warning Icon in the indicators
column and sometimes users do not or cannot see the indicator column if they
have either edited the Entry table to exclude the indicators column or are in
a different table that does not display the Indicators column.

 

[Steve House [MVP]]

Sort of ... I like to think of the practical difference as when you have a
task that's running late, with a FNLT constraint your Gantt chart always
shows it ending on the date where you'd LIKE it to finish but leaves you
totally in the dark as to what it's really doing, while with a deadline, the
Gantt chart show you where it's really GOING to finish if you proceed with
the present plan and flags the spot where it ought to finish so you can
readily see the gap between desire and reality in time to fix the problem.

 

[Eric M]

Steve, that's only true if you have "Tasks will always honor their constraint
dates" selected (checked) on the Schedule tab of the of the Options dialog
box. (Under menu command Tools/Options.) If it is DEselected, and using the
Gantt formatting Dominic suggested, the negative float wll show on the Gantt
chart, showing exactly how much you've missed your constraint by. The
indicator column will also show the warning symbol. I prefer to keep this
deselected and show the negative float - keeps the visual honest!

I know the Bar Styles formatting dialog also has an option to use "Negative
Slack" in the From and To fields, but I've not figured out how to use them
successfully. Anyone who can enlighten me please do so - the onscreen Help is
worthless on that point.

Sort of ... I like to think of the practical difference as when you have a
task that's running late, with a FNLT constraint your Gantt chart always
shows it ending on the date where you'd LIKE it to finish but leaves you
totally in the dark as to what it's really doing, while with a deadline, the
Gantt chart show you where it's really GOING to finish if you proceed with
the present plan and flags the spot where it ought to finish so you can
readily see the gap between desire and reality in time to fix the problem.
--
Steve House [Project MVP]
MS Project Trainer & Consultant
Visit http://www.mvps.org/project/faqs.htm for the FAQs

Dominic,
Thank you. A Negative Slack bar now displays nicely. You illuminated
Format Bar Styles for me.

A deadline on the last task acts like a FNLT constraint, yes?

 

[Jan De Messemaeker]

Hi,

I found 2 ways to display Negative Slack. Try these:

From Negative Slack to Start (positions negative slack BEFORE the task,
tells you when you should start)
From Late Finish to Finish (positions negative slack within the task bar,
tels you when you should finish)

HTH

--
Jan De Messemaeker
Microsoft Project Most Valuable Professional
+32 495 300 620
For availability check:
http://users.online.be/prom-ade/Calendar.pdf

Steve, that's only true if you have "Tasks will always honor their
constraint
dates" selected (checked) on the Schedule tab of the of the Options dialog
box. (Under menu command Tools/Options.) If it is DEselected, and using
the
Gantt formatting Dominic suggested, the negative float wll show on the
Gantt
chart, showing exactly how much you've missed your constraint by. The
indicator column will also show the warning symbol. I prefer to keep this
deselected and show the negative float - keeps the visual honest!

I know the Bar Styles formatting dialog also has an option to use
"Negative
Slack" in the From and To fields, but I've not figured out how to use them
successfully. Anyone who can enlighten me please do so - the onscreen Help
is
worthless on that point.

Sort of ... I like to think of the practical difference as when you have
a
task that's running late, with a FNLT constraint your Gantt chart always
shows it ending on the date where you'd LIKE it to finish but leaves you
totally in the dark as to what it's really doing, while with a deadline,
the
Gantt chart show you where it's really GOING to finish if you proceed
with
the present plan and flags the spot where it ought to finish so you can
readily see the gap between desire and reality in time to fix the
problem.
--
Steve House [Project MVP]
MS Project Trainer & Consultant
Visit http://www.mvps.org/project/faqs.htm for the FAQs

Dominic,
Thank you. A Negative Slack bar now displays nicely. You illuminated
Format Bar Styles for me.

A deadline on the last task acts like a FNLT constraint, yes?

 

[Steve House]

I agree completely with keeping the visuals honest, that's why I use a
Deadline entry instead of a FNLT constraint to indicate the required
delivery dates. IF you turn off the "Task Obey Constraints...." setting as
you suggest, it disables obdience to contstraints globally, including tasks
that really ought to be obeying them in the schedule. Things like a Start
No Earlier Than constraint that's in there to legitimately model the
delivery dates of backordered parts, for example, will no longer place that
task starting after the parts arrive. Instead, the task will show starting
where links and resource availability put it, even if that date is BEFORE
the required parts will be delivered and it really should be on-hold waiting
for them. In terms of calculating the slack for display in the Slack field
of a data table, a FNLT constraint with "Obey Constraints.." turned off and
a Deadline entry with "Obey Constraints..." turned on come up with the same
negative number.
--
Steve House
MS Project Trainer & Consultant

Steve, that's only true if you have "Tasks will always honor their
constraint
dates" selected (checked) on the Schedule tab of the of the Options dialog
box. (Under menu command Tools/Options.) If it is DEselected, and using
the
Gantt formatting Dominic suggested, the negative float wll show on the
Gantt
chart, showing exactly how much you've missed your constraint by. The
indicator column will also show the warning symbol. I prefer to keep this
deselected and show the negative float - keeps the visual honest!

I know the Bar Styles formatting dialog also has an option to use
"Negative
Slack" in the From and To fields, but I've not figured out how to use them
successfully. Anyone who can enlighten me please do so - the onscreen Help
is
worthless on that point.

Sort of ... I like to think of the practical difference as when you have
a
task that's running late, with a FNLT constraint your Gantt chart always
shows it ending on the date where you'd LIKE it to finish but leaves you
totally in the dark as to what it's really doing, while with a deadline,
the
Gantt chart show you where it's really GOING to finish if you proceed
with
the present plan and flags the spot where it ought to finish so you can
readily see the gap between desire and reality in time to fix the
problem.
--
Steve House [Project MVP]
MS Project Trainer & Consultant
Visit http://www.mvps.org/project/faqs.htm for the FAQs

Dominic,
Thank you. A Negative Slack bar now displays nicely. You illuminated
Format Bar Styles for me.

A deadline on the last task acts like a FNLT constraint, yes?