Oracle Primavera P6 PPM Critical Path Calculations

by | Dec 16, 2021 | Critical Path, Oracle Primavera P6 PPM

Many building and construction contracts specify that a delay may only be claimed when it impacts activities on the Critical Path but in turn leave it up to the contractor to decide what scheduling options they may use in their scheduling software, thus allowing the contractor to determine how the Critical Path is calculated. Therefore an understanding how the P6 Schedule Options may assist a contractor to set up their programs to put more activities on the Critical Path and to be able to substantiate more claims than a program with the P6 Default Schedule Options is an important subject.

The aim of this paper is to explain how the P6 Schedule Options affect the calculation of the Critical Path of a P6 schedule and identify which options may be useful for contractors to increase the number of client delays they may be able to substantiate with their schedule, click on this link>>>.

After resource overloads or inefficiencies have been identified with Resource and Tables, the schedule may now have to be leveled to reduce peaks in resource demands. Leveling is defined as delaying activities until resources become available.

There are several methods of delaying activities to level a schedule:

  • Turning off Automatic Calculation and Dragging Activities. This option does not maintain a critical path and reverts to the original schedule when recalculated. This option should not be used when a contract requires a critical path schedule to be maintained, as the schedule will no longer calculate correctly.
  • Constraining Activities. A constraint may be applied to delay an activity until the date that the resource becomes available from a higher priority activity. This is not a recommended method because the delay of the higher priority activity may unlevel the schedule.
  • Sequencing Logic. Relationships may be applied to activities sharing the same resource(s) in the order of their priority. In this process, a resource-driven critical path is generated. If the first activity in a chain is delayed, then the chain of activities will be delayed. But the schedule will not become unleveled and the critical path will be maintained. In this situation, a successor activity may be able to take place earlier and the logic will have to be manually edited.
  • Leveling Function. The software Resource Leveling function levels resources by delaying activities without the need for Constraints or Logic and finds the optimum order for the activities based on user defined parameters. Again, as this option does not maintain a critical path developed by durations and relationships, it should not be used when a contract requires a critical path schedule developed in this way. The Leveling function may be used to establish an optimum scheduling sequence and then Sequencing Logic applied to hold the leveled dates and to create a critical path.

The Resource Leveling function enables the optimization of resource use by delaying activities until resources become available, thus reducing the peaks in resource requirements. This feature may extend the length of a project.

The leveling function should be used by novices with extreme caution.

  • It requires the scheduler to have a solid understanding of how the software resourcing functions calculate.
  • Leveling increases the complexity of a schedule and requires a different approach to building a schedule. In principle, the sequencing logic is replaced by Priorities but a Closed Network should still be maintained.

Your ability to understand how the software operates is important for you to be able to utilize the leveling function with confidence on larger schedules. It is recommended that you practice with small simple schedules to gain experience in leveling and develop an understanding of the leveling issues before attempting a complex schedule.

Accelerate your understanding of scheduling software to advance your scheduling career and be able to prepare better schedules with Eastwood Harris books, online videos available through Udemy and training material on:

Details at

Paul E Harris

Director Eastwood Harris Pty Ltd