Hi,
Any suggestion on where to find a well-detailed explanation of how the lag between different activities in P6 are scheduled?
I am experiencing some strange behaviors in particular cases, for which I am not able to provide a rational explanation.
e.g. :if I select the successor´s calendar for scheduling the lag between two activities with different calendars, I see that the days are converted any case in hours following the calendar of the predecessor. This seems counter-intuitive to me but I can´t find the setting to change it. I would like to understand if there is a specific reason for this, as I can´t see it myself.
Hi Giocomo,
Below articles may be helpful for Lead and Lag time calculations.
https://www.projectcubicle.com/lead-and-lag-time-in-project-scheduling/
https://www.projectcubicle.com/primavera-p6-relationships/
https://www.projectcubicle.com/precedence-diagram-method/
Even when the software works 100% correctly there are problems in the PDM approach to tasks and links that will cause issues if you are unaware of them for an explanation see: https://mosaicprojects.com.au/PDF/Links_Lags_Ladders.pdf
When you do understand the options you can do some lovely 'party tricks' to confuse the opposition... :-)
The durations will always be stored in hours, then it uses the calendar settings to convert that value to days / weeks / etc.
As the number of hours that a day represents is dependant on the settings as defined in each of the calendar settings, so a day can be equal to anything between 0 & 24 hours in duration.
An hour will always be an hour, so the calculations are all based on this.
All durations are stored in hours regardless of your user preference settings, not just the Lag values.
If you have a calendar based on a 6 hour working day & your user preferences are set to enter durations as days then Primavera will save 1 day as 6 hours in the Database.
This is why it is important to correctly set the time periods when creating a calendar.
Steven
Thanks Tom,
let´s see if the functionality will be implemented in a future version.
I was trying to use the successor´s calendar for the relationship calculations, but considering this I think it´s better if I stick to the predecessor "classic" settings.
Thanks Tom,
let´s see if the functionality will be implemented in a future version.
I was trying to use the successor´s calendar for the relationship calculations, but considering this I think it´s better if I stick to the predecessor "classic" settings.
Primavera has no "elapsed time" facilities. Everything is Calendar based, and in hours. I keep track of Lags (which are horrible in Primavera, hard to report on, won't show in a barchart, can't see what they were in a baseline, they are essentially invisible) by always having the "scheduling options" setting to use the 24 hour calendar to calculate lags, and always enter them as hours. Even if my durations setting is "days" I would enter a two day lag as "48h" - of course this will be translated by Primavera as a number of days in the layout BUT it has stored 48 in the database, and my Lags option for scheduling always makes that 2 wall-clock days.
I have seen the same thing, and there's no way to change it. I.e. the lag is stored in hours, and the unit conversion (when specifying or displaying the lag) is always according to the Time Periods of the predecessor calendar (or the default Time Periods if calendars are ignored.)
The unit conversion is not part of the schedule calculations. It is not affected by the schedule options selection.
go to
tools
schedule
options
then at the bottom of the page you can set what calendat that you want to use for scheduling the relationship lag.
your choices are
24 hour calendar
predecessor activity calendar
or
successor activity calendar
each of these will provide different results see what works best in your case
Primavera does all of its calculations in hours. You can see durations, and resource quantities, and float and lags in days, but that is a display-time conversion from the hours which is how the data is stored. There is no option to calculate in days.