Limited application of positive lag is acceptable in most scheduling guidelines. The P6 scheduler should inspect each instance of schedule lag in Primavera P6 for proper usage.
Note the positive qualifier. Positive lag and not negative lag is agreeable to most scheduling guidelines. Negative lag is forbidden by many scheduling guidelines, including the Defense Contract Management Agency (DCMA) 14-Point Assessment guidelines. Judicious use of positive lag, again, is acceptable.
One reason wide implementation of positive lag is discouraged is because lag is less transparent. Lag, either positive or negative appears on the Gantt chart as a line with little to no identifier or labeling. The scheduler should inspect each instance of lag and confirm the process being modeled.
This article demonstrates a quick tip on how to highlight all activities in the Primavera P6 Professional schedule that have relationships with lag qualifiers.
The most comprehensive (or tried and true) way to investigate and report schedule lag is by creating a Primavera P6 Professional report. Refer to the following blog Investigating Relationship Lag in Primavera P6 for instructions on creating an activity lag report.
Creating a report is the recommended approach. A lesser tested approach to inspecting lag is to filter and highlight lag in the activities table. Although this approach is the most efficient way to highlight schedule lag it comes with a few caveats:
- The filter captures the “d” identifier, so Activity IDs cannot contain the letter d, either upper or lower case
- In the user preferences duration format you must toggle on ‘show duration labels’
- It requires Primavera P6 Professional version 16.1 or later
We have in Figure 1 our demonstration project.
Figure 1
This schedule has a few activity relationships that have lag qualifiers. It, however, is very difficult to perceive which activities in the activity table or Gantt chart have the relationship lag qualifiers. Again, you can create an activity lag report as mentioned above. However, to quickly highlight all activities that have successor relationships and lag qualifiers use a lag filter.
First we display the successor details column in the activity table, Figure 2.
Figure 2
If you review the successor details column closely you may note lags listed in this column. Look for numbers that include the suffix ‘d’. This suffix ‘d’ identifies the number as a lag value because it picks up on the ‘d’ suffix of the number of days. You may, however, have to strain your eyes to correctly spot relationships with lag qualifiers. It is quicker to create the filter displayed in Figure 3.
Figure 3
The parameter in this filter is ‘successor details’, the equivalency is ‘contains’, and the value ‘d’. This filter simply logs all activities that have successor details containing the lowercase ‘d’. Because we want to inspect how these lag qualified relationships connect into the schedule we highlight them and do not replace them. Toggle ‘highlight activities in current layout which match criteria’, Figure 4.
Figure 4
Select OK and the resulting activity table highlighting activities that include relationships with lag for our demonstration schedule is displayed in Figure 5.
Figure 5
Now all activities that have lag relationship qualifiers are highlighted.
Summary
Too much lag makes a schedule static and not dynamic. Manual lag updates are required each time activity durations change. Lags are also not very transparent. Lag should come with some note or documentation to explain its purpose.
To investigate lag in the schedule, we recommend creating an activity lag report using the report features in Primavera P6 Professional. However, it you just want to quickly spot activities in the schedule that include relationships with lag qualifiers create a simple filter and toggle the filter highlight option.