A Lag is a duration that is applied to a dependency to make
the successor start or finish earlier or later.
A successor activity will start later when a positive Lag is
assigned. Therefore, an activity requiring a 3-day delay
between the finish of one activity and start of another will
require a positive lag of 3 days.
Conversely, a lag may be negative when a new activity may
be started before the predecessor activity is finished. This is
called a Lead or Negative Lag.
Leads and Lags may be applied to any relationship type.
Here are some important points to understand about Lags:
The lag duration is calculated on the lag as in Microsoft
Project and other Primavera products. A lag is not
assigned to one or both of the Predecessor and Successor
activities as in Asta Powerproject.
Lags may be assigned one of four calendars from
the Calendar for Scheduling Relationship lag drop down
box in the General Schedule Options form. This form is
opened by selecting Tools, Schedule… and clicking on
the tab. The four Lag Calendar options are:
Predecessor Activity Calendar,
Successor Activity Calendar,
24-Hour Calendar, and
Project Default Calendar.
Lags are calculated by Primavera P3 and SureTrak
software using the Predecessor Calendar. Microsoft
Project 2003 to 2010 uses the Successor Calendar or may
have an Elapsed Duration Lag. Earlier versions of Microsoft
Project used the Project Calendar.
Asta Powerproject assigns the lag to either or both the
predecessor or successor thus allowing either the
Predecessor or Successor Calendar to be selected for each
You must be careful when using a lag to allow for
delays such as curing concrete when the Lag
Calendar is not a seven-day calendar. Because this
type of activity lapses nonwork days, the activity
could finish before Primavera calculated finish date.
You must be extremely careful when opening multiple
projects when the Lag Calendar option is different for each
project. This is because all the project options are changed
permanently to be the same as the Default Project and
therefore some of your projects may not calculate the
same way as they did before opening the projects together.
Please read the Multiple Project Scheduling chapter for
more details on this topic.
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