Out-of-Sequence (OOS) activity is an activity for which its relationship has been violated, as shown in the image below:
In the example above, activity B had FS relationship with activity C. However, activity C has been updated and assigned an actual start date before Activity B.
How Out of Sequence Activity is Managed?
OOS logic should be corrected to preserve the integrity of the schedule model unless OOS for the activity was really necessary. Often, planned sequence is not correct, hence OOS logic is retained. Out of sequence activity can be implemented in two ways:
Retained Logic is recommended to comply with activity relationship to some extent.
Retained Logic, Progressive Override options can be set in Primavera software.
See the image at right for better understanding of progress override and retained logic options.