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TOTAL FLOAT CALCULATION IN PROJECT MANAGEMENT (P6.2)

12 replies [Last post]
Mohammad Irfan Ah...
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Is it possible to have total float (negative float) longger than my current project duration.

For Example :

- I have develop 5 years program for 1 project
- The project progressing for 1 year
- Is it possible to have total float (negative float) bigger than 1 year?

How it’s happen and how to rectify this.

Replies

Dieter Wambach
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Posts: 1350
Irfan

Without knowing the project it’s rather difficult for me. The year "2006" must have an origin.

Did you check in the view "projects" the tab "Dates". Is there a "Must finish by"? Remove it.
Check the log file for "out of sequence" and for "unsatisfied constraints" and for "unsatisfied relationships".

Regards
Dieter
Mohammad Irfan Ah...
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I have checked the constraint and removed all the constraint, except for first activities i used "Start On or After" and Last activity that i have used "Finish On or After". The result still same.....

I have also checked all the actual start and actual finish date..... i have not found any date at 2006.....

I will keep trying analyse this program.....

By the way most of the people here call me Irfan....

Regards;

Irfan
Dieter Wambach
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Late date in 2006 means that there should be a constraint or an actual for 2006. What does the logfile of scheduling say?

Another item are SS and FF relationships. Standard should be FS.

Which option do you use for schedule, retained logic or actual dates?

Regards
Dieter

By the way, what’s the name people call you?
Mohammad Irfan Ah...
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I have done something;

The float in the programme showed very big gap between each related activities. For Example....

Activity 1 linked to Activity 2 with SS Relationship

Activity 2 linked to Activity 3 with FF Relationship

Activity 3 linked to Activity 4 with FF Relationship

Total Float at Activity 1 & 2 showed only negative 4 Months float but the activity 3 and all subsequent activity showed negative 2 years float.

It’s have a big gap between the activities. The activity have no other link to others activities.

I’m curious from where this float coming.

I have checked all the date, it showed that activity 3 & 4 late date (late start & late finish) has move behind.

My project planned to start at Jan 2008 and have actual start on the same date.

The late date for this Activity 3 & 4 showed the late date at 2 years behind. It means Jan 2006. This given the negative 2 years float.
Rafael Davila
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CPM Schedules properly updated, either with progress override or retained logic options should yield the same results, otherwise CPM theory is nonsense/(BS).
You should, under either option, revise schedule logic and make appropiate logic adjustments.
The owner should recognize you have the right (shall I say obligation) to do so, otherwise it is the owner who is preventing you from submitting a true schedule. At any time if your company feels the schedule logic should be changed you should be free to do so. The Owner should not control your "Means and Methods", but he has the right to know and to protect himself from ureasonable claims.
This is an issue you must resolve as soon as it happens during your updates. If the schedule does not represent the true sequence it might be questioned later during your claim evaluation.
By the way I prefer the method of Progress Override.
Mohammad Irfan Ah...
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Thanks guy for the advice, i will try it first and come back to you with the result.
Dieter Wambach
User offline. Last seen 6 years 49 weeks ago. Offline
Joined: 15 Jan 2007
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Did you check one of those activities with "Trace Logic"?
The boxes should contain: Id, name, early start& finish, primary constraint, constraint date, total float. Using trace logic you can easily see the development of the float. I have some doubts for a wrong constraint date.
Good luck!

Gary
No problem to delete and recreate an actvity without actual units. Just required to use the same Id. Then it will be referenced to the baseline.

Regards
Dieter
Gary Whitehead
User offline. Last seen 4 years 43 weeks ago. Offline
if you’ve only got 10-20 activities that are causing the problem, I’d avise going through each one in turn and comparing it vs the baseline program. look for any changes to:
constraints / targets
logic & lags
duration
activity type
resources

To get negative float larger than time elapses, one of these things must have changed, IMO.

The only other thing I can think of is some kind of bug in the system. I’ve never used P6.2 in anger, but you could try taking a copy of the project, deleting the offending activitites, then adding them again to see if that helps -though that will make comparing vs baseline tricky going forward.
Mohammad Irfan Ah...
User offline. Last seen 10 years 7 weeks ago. Offline
Joined: 27 Apr 2007
Posts: 26
Groups: GPC Malaysia
i have tried this option, it resolve for some activities but still have 10 - 20 activities with huge negative float.

i try not to used progress override, this will affect my Extension of Time application later.

any other solution for this....
Gary Whitehead
User offline. Last seen 4 years 43 weeks ago. Offline
under scheduling, options, try ticking the ’progress overide’ box instead of retained logic.
This should help, but I’m still not sure how the total negative float has become larger than the time elapsed unless something else has happened rather than merely out-of-sequence working.

To explain difference between progress overide & retained logic:
if activities ABC are scheduled in sequence using FS relationships, and during progress update you say B has been completed, but A has not:
-retained logic option will say C cannot start until A is completed
-progress overide will say C could start from date B was completed

Be very careful with using progress overide, as it can have unintended consequences eg in the example above if C in the ’real world’ cannot start until both A and B are finished, it will give you the wrong result unless you also have a FS relationship between A and C
Mohammad Irfan Ah...
User offline. Last seen 10 years 7 weeks ago. Offline
Joined: 27 Apr 2007
Posts: 26
Groups: GPC Malaysia
Thanks Gary;

- First of all when i originally developed the program there was no negative float

- The huge negative float start appearing when we start progress with out of sequence activities. The negative float showed double compared with the current project progress

- I have carry out an analysis on the activities that showed huge negative float and it’s look like the late date has moving backward (it’s move up to 2 years before project start or planned to start) while early date moving forward. This give a result of huge negative float.

- From what i know, the late date suppose to be between first start date and last finish date or until "must finish by" date.
Gary Whitehead
User offline. Last seen 4 years 43 weeks ago. Offline
something’s clearly gone very wrong somewhere.
Presumably when you originally developed the program, there was no negative float? If so, here’s some things to look into:

1) when did the negative float start appearing? has it ’grown’ gradually over the year, or did it appear all at once?
2) Have you made any changes to logic or planned durations?
3) Have you added or changed any constraints?
4) Does the project have a target finish date? Is it correct?
5) Can you find the (most) critical path in the program? Trace it through activity by activity to try and find the ’offending’ activity
6) Do you have an older version of the program from before the negative float started appearing? If you apply all actual progress to that program, do you get the same result?
7) Is anyone else able to make changes to the program? Do you have an audit trail?
8) Have you made any global changes which may have gone wrong?