How to Dissolve an Activity in Primavera P6 Professional

What happens when you have a sequence of activities and you need to remove one of the activities? Normally in the Primavera P6 Professional project management software, you would manually delete the activity that is no longer needed, then you would link any of its predecessor activities to its successor activities. For example, in Figure 1 below, when Activity B is removed, then Activity A and Activity C are then manually connected with a Finish-to-Start relationship.

Figure 1: Primavera P6 – What is Dissolve an Activity

What is “Dissolve an Activity” in Primavera P6

There is an option available in Primavera P6 called Dissolve. Dissolving an activity removes the activity then joins the dissolved activity’s predecessor and successor activities. The four possible Relationship Types available are: Finish-to-Start (FS), Start-to-Start (SS), Finish-to-Finish (FF) and Start-to-Finish (SF). 

Guildelines for the Dissolve process can be found in Oracle Primavera’s online help documentation at: Oracle Primavera P6 Help

Some of the rules are:

• An activity cannot be Dissolved if it does not have both a Predecessor or Successor activity.
• Primavera will try to preserve the relationship network logic.
• When an activity is dissolved, it will connect any of its direct predecessors to all of the dissolved activity’s successors. It will use the same relationship types (ex, Finish-to-Start, Start-to-Start, Finish-to-Finish, Start-to-Finish) that existed between the predecessors of the dissolved activity.
• When an activity is dissolved, it will connect any of its direct successors to all of the dissolved activity’s predecessors. It will use the same relationship types (ex, Finish-to-Start, Start-to-Start, Finish-to-Finish, Start-to-Finish) that existed between the successors of the dissolved activity.

Figure 2 shows an example project scenario before we Dissolve Activity C.

Activity C’s Predecessors:

• Activity B has a Finish-to-Start (FS) relationship with Activity C
• Activity D has a Start-to-Start (SS) relationship with Activity C

Activity C’s Successors:

• Activity C has a Finish-to-Start (FS) relationship with Activity E
• Activity C has a Finish-to-Finish (FF) relationship with Activity F

Figure 2: Primavera P6 – Sample project scenario

How to Dissolve an Activity

Figure 3 below outlines the steps to Dissolve an Activity. First select the activity you want to remove, in this example, Activity C. Next right-click the mouse over top of the activity to bring up a sub-menu. Select “Dissolve”. You will be prompted “Are you sure you want to dissolve the selected activity?  This cannot be undone.” It is highly recommended to make a backup copy of your project before dissolving an activity just in case you didn’t need to remove the activity or did not like the outcome. Click the “Yes” button to confirm.

Figure 3: Primavera P6 – How to Dissolve an Activity

Figure 4 shows the example project’s results with Activity C removed. Notice how the positions of the other activities have not moved yet. The project will need to be scheduled in order for Primavera to recalculate the Start and Finish times of the activities.

Figure 4: Primavera P6 – Sample project after Dissolve, before Scheduling

The results after scheduling the project are shown in Figure 5. As you can see, the logic of the project was preserved as well as possible with the removal of the activity.

Figure 5: Primavera P6 – Sample project after Scheduling

Summary

The Dissolve Activity function in Primavera P6 works well to help remove an activity while maintaining the relationship connections and logic of the project. It is advisable to backup the project plan before permanently dissolving the activity because you cannot undo the activity deletion.

To learn more about the Predecessor Details and Successor Details Columns in this article https://www.p6consulting.ca/blog/relationship-details-columns-in-primavera-p6-professional/

For a full overview of our project management online training classes via the Primavera P6 software, visit our Training Courses page.

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