As a Primavera P6 Professional and Oracle Primavera Cloud trainer, I often assist users with project issues. One common question I receive relates to schedule drift. This is where an activity’s data changes unexpectedly after scheduling. Most commonly, you’ll see this during status updates. While scheduling the project, activity’s finish date or duration may change without prompt.
In Primavera programs, this often occurs due to improper scheduling techniques. If not resolved, this can lead to significant project delays and increased durations.
There is a simple solution to this problem, and it comes from understanding how the Primavera scheduler works. In this article, we will take a look why schedule drift can occur and what to do to prevent it.
The following examples are taken from Primavera P6 Professional. The scheduling principles discussed will also apply to other Primavera schedule management programs, including Oracle Primavera Cloud and Primavera P6 EPPM.
The Problem: Schedule Drift and Increased Durations
The root cause of this issue lies in users trying to schedule in P6 the way that they would in Microsoft Project. These programs function quite differently – especially in regards to the schedule tool. It is recommended that users transitioning to P6 undergo training to fully understand how the program operates. Knowledge of MS Project alone is insufficient for scheduling in Primavera P6.
When using the Schedule tool in P6, the program will use the Critical Path Method algorithm to calculate planned dates for each activity. This calculation will look at activity durations and relationships to determine ideal dates. The Schedule tool will ensure that all activities can be completed within the set time frame. Once the project starts, the user will need to update the activities with actual data – such as the Actual Start and Actual Finish dates. By comparing these actuals with the planned dates, you can assess whether the project is ahead, behind, or on schedule.
Schedule drift can occur when users improperly perform status updates. Let’s take a look at an example. Below, I have an activity called Rough Grade. This activity has 10 days of duration and a planned start date of January 25th.
This outcome occurred because I didn’t use the scheduler properly. Let’s delve into how the P6 scheduler operates to understand this situation better. To revert the activities back to their original dates, I can schedule the project again and change the Data Date back to January 1st.
Understanding How the Primavera P6 Scheduler Works
How to Properly Update Activities
Using the Data Date
After scheduling the project, the completed activity, Trench for Utility Lines, did not move. Setting actual dates to an activity will lock it in place. However, all the activities that were supposed to start in January – but did not – were pushed forward by the Data Date. The program is assuming that these activities did not get done during January, but still need to be completed. Therefore, the program calculated a new start and finish date for those activities.
Accounting for Activity Progress
Schedule drift in Primavera programs is almost always due to a misunderstanding of how the schedule tool works. In Primavera P6, Oracle Primavera Cloud, and Primavera P6 EPPM, you need to make sure that you provide as much information as possible about the updated activities. Not only will you need to enter in the activity’s actual starts and finishes, you will also need to report progress for in progress activities. Additionally, you’ll need to be aware of how the data date works. You should only ever move the data date once all activities prior to the update date have been statused.
When performing status updates in Primavera programs, you should follow this order of operations:
- Gather all information from users on the field. Make sure you know when activities have started, have finished, and the progress of activities that are ongoing.Before performing a status update, make sure you have a saved baseline of the project’s current version.
- Identify the activities that need to be updated within the schedule. You can do this with the use of a Lookahead Filter or the Progress Spotlight tool.
- For each activity you’re updating, enter in an Actual Start date if the activity has started. If the activity has finished, enter in an Actual Finish date. If the activity is ongoing, enter in either an Expected Finish date, a Remaining Duration, or a % Complete value.
- If the activities have resources, costs or units assigned to them, enter in those actual values, as well.
- Once you have updated all activities within the update period, schedule the project by selecting Tools > Schedule. Move the Data Date to the date you have statused the project up to.
- Once completed, create another baseline to save the project as it is.
If you follow these instructions for each update period, you will avoid common schedule issues like drift and delays.
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Lauren Hecker is a Primavera P6 Professional and Oracle Primavera Cloud Instructor. She teaches onsite and virtual Primavera P6 and OPC training courses. To see her next open enrollment course, please visit our calendar. To schedule an onsite or custom course, please contact us!