Ramakrishna
The reason for the negative float is normally in the whole structure of your network, i.e. the activites itself, the relationships, work centers in the activities, durations, etc. In principle the system allows creating nearly all kinds of stucturs with complicated relationships, independent of whether the relationships make any sense or not.
What the system does when you schedule is the following:
If you have selected a forward scheduling scheme, it executes a forward scheduling from the entered basic start date, and determines the earliest end date.
Then the subsequent backward scheduling is executed from this scheduled end date, and the latest start date is determined.
In other words, the dates of the earliest dates result from forward scheduling. The dates of the latest dates result from backward scheduling.
If you have selected 'backwards scheduling', the procedure will be the same but starting with the backward scheduling and then performing the forward scheduling.
In your case, due to the relationships and so on, the latest
start date can be before the earliest start date (a backwards run would
take more time so to say) and therefore, simultaniously the total float of some activities, which simply is the latest start date minus the earliest start date, is negative.
So to conclude, the negative float is not an error, but the result of your network and settings.
Hope this helps
Martina
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