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total float in negative for critical activities

21 replies [Last post]
Mon, 2008-07-07 02:20
faisal afsar
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i have made a plan in which many of the activities are showing total float in the negative how come it is possible can somebody explain this to me a dn all these activities are critical activities. plz explain this to me
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Thu, 2013-04-25 12:05
#1
Jaimin Shah
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If it is happening in MS Project, change the project start date to any.

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Wed, 2008-07-09 05:23
#2
Darren Kosa
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Faisal,

Have all your tasks been progressed to a status date?

Are there any Finish-Start tasks in the schedule where a task successor has a value greater than 0% Complete, but the predecessor is not 100% Complete?

If a successor is 5% Complete for example, it will have an Actual Start. This means that the start of the task has been fixed to that date and will not move (similar to a Must Start On constraint).

If the predecessor task isn’t complete and the Finish date moves past the Actual Start of its successor task, then it will show negative values in the Total Slack column. This may also account for the numbers after the decimal point.

Regards,

Darren
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Wed, 2008-07-09 03:30
#3
Trevor Rabey
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One bridge at a time.
First fix neg total slack.
decimals are a different problem. Fix that next.
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Wed, 2008-07-09 02:39
#4
faisal afsar
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my dear tom dick and harry pls read read the post carefully is is coming in decimals as well
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Wed, 2008-07-09 01:12
#5
faisal afsar
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i have removed the date constraints and the deadlines also
but still it persists the predecessors are there but no negative lag
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Wed, 2008-07-09 01:03
#6
Trevor Rabey
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This question was answered several times, some time ago.
There are only two possible causes of negative total slack:
1) Date Constraints
2) Deadlines

Can you please confirm that you have shown the columns amended the plan so that you have none of either?

Not thought to be a direct cause compared to above, but worth checking anyway, do you have SS, SF, FF predecessor links and/or negative lag?
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Wed, 2008-07-09 00:47
#7
faisal afsar
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tasks in the total slack have negative values as well in decimal like -25.13 days/-28.13 days

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Tue, 2008-07-08 09:54
#8
Darren Kosa
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Faisal,

OK I’m confused… what is the problem?

Tasks in the Total Slack column have values that = -16d / -20d etc.

Or

Tasks in the Total Slack column have values that = 16.27d / 5.65d etc.

If it is Total Slack = -16d / -20d, have you looked at all the suggestions in post #14? If it is Total Slack = 16.27d / 5.65d, is your schedule effort driven and / or do you have split tasks?

Regards,

Darren
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Tue, 2008-07-08 08:51
#9
faisal afsar
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dear darren
the negative values for total slack for critical activities still persists
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Tue, 2008-07-08 07:06
#10
Darren Kosa
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Faisal,

The majority of the time, Total Slack is displayed as whole numbers (days / hours / etc.), but occasionally the Start / Finish dates of tasks don’t exactly match the default Start / End times. This is most likely the cause of your problem.

You need to check to see if this is the case

Go to Tools > Options > Calendar and make a note of the default Start / End times.

Then go Tools > Options > View and change the date format to include hh/mm.

When you look at your schedule in the Gantt View, your Start / Finish dates should look something like this… Tue 08/07/08 08:00.

All you then have to do is scroll through the tasks and look at the hh/mm part of the Start / Finish dates. When you find any times that look something like Tue 08/07/08 08:17, work your way back through the network until you find the offending task and decide what you have to do with it.

Sometimes this is caused by resource work (effort driven) increasing or decreasing the Duration value, other times because split tasks change the Duration and Start / End values by rescheduling uncompleted work to start after the status date.

Regards,

Darren
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Tue, 2008-07-08 05:43
#11
faisal afsar
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thanks darren it rectified one of the task in the ddadline column had a date i made it to NA no there are no negative date ... but there is one problem some of the total slack arecoming in decimals
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Tue, 2008-07-08 04:56
#12
Darren Kosa
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Faisal,

Let me make sure I understand you correctly.

1) In the Constraint Date column ALL tasks are ‘NA’
2) In the Constraint Type column ALL tasks are ‘As Soon As Possible’
3) In the Deadline column ALL tasks are ‘NA’

Is this correct?

Also a few more questions…

1) Is your project scheduled from the project finish date? (Project > Project Information)
2) Are there any external links in your project to other projects that have hard constraints?
3) Have you added any VBA code that that uses / changes any of the Start / Finish / Duration / Constraint fields?

Regards,

Darren
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Tue, 2008-07-08 01:05
#13
faisal afsar
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yaara its total slack
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Tue, 2008-07-08 00:54
#14
faisal afsar
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total float
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Tue, 2008-07-08 00:42
#15
faisal afsar
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i have checked it nothings is wrong
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Tue, 2008-07-08 00:32
#16
faisal afsar
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i have doe it what u said but still the negative days persists it is not being removed
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Mon, 2008-07-07 09:58
#17
Darren Kosa
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Hi Faisal,

Insert the ‘Constraint Type’ and ‘Constraint Date’ columns. Ideally all tasks (apart from the start activity) should have a flexible constraint (As Soon As Possible or As Late As Possible).

The constraints that are probably giving you negative slack are the hard constraints (Must Start On or Must Finish On). Look down the column or use a filter to isolate these tasks and decide whether it needs a new constraint type or you need to change the constraint date.

Regards,

Darren
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Mon, 2008-07-07 09:20
#18
faisal afsar
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its not happening
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Mon, 2008-07-07 09:05
#19
Pranab Kumar Deb
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PUT "NA" IN PLACE OF DATE IN TASK INFORMATION>ADVANCED-CONSTRAINT DATE.
REGARDS
DEB
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Mon, 2008-07-07 08:50
#20
faisal afsar
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Trevor

How to remove the constraints plz say
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Mon, 2008-07-07 07:57
#21
Trevor Rabey
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Some Task or Tasks somewhere in the critical path have either date constraints which are earlier than their "natural starts and finishes, or deadlines which are earlier than their finishes, or both, and so all of their predecessors therefore have negative lag.
Since I cannot see how many date constraints you have or where they are, same for deadlines, I can’t say which ones to fix, but the first thing I would do is remove all of them.
Both the Date Constraints and Deadlines show up in the indicators column or can be seen in the Date Constraints and Deadlines columns.
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