Is there a way in Primavera P6 Professional to remove an activity and maintain schedule logic continuity? Yes, there is. It’s done by dissolving an activity instead of deleting that activity.
Schedules often require updates and changes as the process of envisioning and planning a project comes together in the Primavera P6 Professional scheduling tool. It is not uncommon for project updates to require deleting a schedule activity.
Deleting an activity, however, often results in discontinuities in logic. The reason is that when an activity is deleted that activities relationships are removed as well. So when the activity is deleted you may be deleting its predecessor’s only successor and its successor’s only predecessor.
This leads to open ends in logic and may cause significant changes to schedule completion dates when the schedule is recalculated. To avoid these logic discontinuities dissolve the respective activity instead of deleting it.
This article demonstrates a quick tip on how to dissolve an activity in Primavera P6 Professional.
We have in Figure 1 our demonstration project schedule.
Figure 1
This schedule is for an underground pipe installation project. It turns out we do not need the install shoring activity. Shoring is required when the respective trench is 6 feet or deeper. The underground pipe installation will only require a 5-foot deep trench, so we can remove the install shoring activity.
Let’s first delete the install shoring activity and see what happens. Right click on install shoring and select delete from the popup menu, Figure 2.
Figure 2
As displayed in Figure 3 install shoring is removed, but now there is a logic discontinuity between backhoe excavate and common laborer excavate.
Figure 3
When we reschedule the project the resulting schedule is displayed in Figure 4, which shows that our schedule was essentially cut in half and the project end date significantly changed.
Figure 4
Now let’s dissolve that same install shoring activity, Figure 5.
Figure 5
The resulting schedule is displayed in Figure 6.
Figure 6
Install shoring was removed and its predecessor and successor linked together. You should note, however, there is a time gap between backhoe excavate and common laborer excavate equivalent to the duration of the dissolved install shoring activity. When we reschedule the project the resulting schedule is displayed in Figure 7.
Figure 7
Note the time gap disappears and there is a slight adjustment to the project end date.
Summary
When you want to remove an activity in Primavera P6 and maintain schedule logic continuity, dissolve that respective activity instead of deleting it. Deleting an activity removes the activity and its logic/relationship ties. Dissolving the activity removes the activity but links its predecessor to its successor to maintain schedule logic continuity.
The activity must have both a predecessor and successor in order to dissolve it. Dissolving works best with finish to start (FS) relationships. It may work well with other relationships, but review links after dissolving to verify correctness.
Dissolving multiple activities simultaneously in Primavera P6 is not available. It is possible to dissolve an activity that has multiple predecessors and successors, but this is not recommended as dissolving an activity with multiple predecessor/successor links breeds confusion.