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An overview of Trace Logic in Primavera P6

Trace Logic is a great tool available in Primavera P6 that allows you to step or “trace” forward or backward through a series of activities in order to view or focus on predecessor/successor relationships. Trace Logic can be displayed as a Bottom Layout in the Activities window. The Trace Logic tool displays relationships for an activity that you select in the Activity Table, Activity Network, Activity Usage Spreadsheet, or the Gantt Chart displayed in the Top Layout. The selected activity will be displayed as a box with a blue border that enables you to quickly focus on its predecessor/successor relationships. Critical activities will be displayed with a red border around the activity box. Lines connecting the activity boxes denote activity relationships.

Why would I use the Trace Logic feature?

Trace Logic can be used by project managers and schedulers to review an activity’s predecessors and successors. Trace Logic makes it easy to examine why an activity is scheduled to occur at a particular time helping you to determine if an activity’s predecessors were delayed or if existing constraints are still applicable. You can quickly evaluate if relationship types portray the sequence in which the activities should occur. For example, you may notice that a Site Prep activity can have a “start to start” relationship with its Excavation successor versus “finish to start”.

This tutorial provides instructions for displaying and customizing the Trace Logic.

Step 1: Open a project & select a layout. The layout selected below is “Current versus Baseline Bars”. Notice that BA2020 Excavation activity started late, has a work stoppage as evidenced by the “bar-neck”, and finished late when compared to its baseline. We will use Trace Logic to determine the possible impact on successor activities.


Step 2: Lets display the Trace Logic on the Bottom Layout by selecting “View”, “Show on Bottom”, “Trace Logic”.

Step 3: Once Trace Logic is displayed in the bottom layout, you can select an Activity in the top layout. The top layout displayed below is the Gantt Chart view (consisting of the Activity Table and the Gantt Chart). We can select an Activity by clicking on the activity in the Activity Table or on the Gantt Chart.

Additional top layout options include:

  • Activity Network
  • Activity Usage Spreadsheet
  • Activity Table

The activity BA2020 Excavation has been selected, and the Trace Logic in the bottom layout displays the predecessors and successors for Excavation. We are able to trace the possible impact of the delay in the Excavation on its successors. Notice that the selected activity is displayed with a blue border in the Trace Logic. Also, notice that activities on the critical path (such as BA2030 and BA2040) are displayed with a red border around the activity box. You can use the zoom-in and zoom-out features to view the trace logic as well as the contents of the activity boxes.

How do I identify critical activities, critical relationships, and driving relationships?

The following visual indicators represent critical activities, critical relationships, and driving relationships:

  • Activity boxes outlined in red are critical activities; activity boxes outlined in black are not critical activities.
  • Solid red lines represent critical relationships, while solid black lines represent non-critical relationships.
  • Solid lines represent driving relationships, while dashed lines represent non-driving relationships.



Step 4a: You can specify the number of levels of predecessors and successors that you want to view by accessing the View menu and selecting Bottom Layout Options. You can also right-click in the Trace Logic display and select Trace Logic Options.

Step 4b: Use Trace Logic Options dialog box to specify the number of levels of predeccessors and successors to display.


Step 5: The activity boxes in Trace Logic display the same information as the boxes defined for the current Activity Network layout.

You can control the contents of the activity boxes by selecting the:

  1. View menu
  2. Activity Network
  3. Activity Network Options



Step 6: The Activity Network Options dialog box allows you to select a “box template”, which will contain activity information. You can edit the box template to change the information displayed.


Step 7: To print the Trace Logic:

  1. access the Print Preview icon from the Toolbar
  2. select the “Page Setup options” tab
  3. mark the “Trace Logic” checkbox and any additional options



Step 8: Sample Trace Logic print preview.


MSS Inc. is a full service project management solutions firm and provides outsource planning, scheduling, and project controls for organizations in project intensive industries. We specialize in Primavera software and have expert consultants and implementation experts. Contact MSS Inc for a FREE software consultation today.