Introduction
The Start-to-Finish (SF) relationship is the least commonly used type of activity relationship in Primavera P6. In this relationship, the successor activity cannot finish until the predecessor activity has started. This type of relationship is useful in special circumstances where one activity’s completion is dependent on the start of another.
The SF relationship is typically used in situations where an activity must continue until another activity starts, ensuring there’s no gap between the two activities.
Key Characteristics of Start-to-Finish (SF) Relationship
- Unusual Dependency:
- Unlike other relationships, the SF relationship is less intuitive and is rarely used in straightforward projects. The successor activity is dependent on the start of the predecessor.
- Opposite of FS:
- The SF relationship is essentially the opposite of the Finish-to-Start (FS) relationship. Instead of waiting for one activity to finish before another starts, it waits for one activity to start before another finishes.
- Strict Coordination:
- The SF relationship ensures that one activity doesn’t finish until another one begins, typically used for coordination of shifts, handoffs, or continuous operations.
Real-Life Examples of SF Relationship
Example 1: Shift Work in a Factory
- Predecessor Activity: Start the night shift.
- Successor Activity: Finish the day shift.
In this scenario, the night shift workers must begin their tasks before the day shift workers can finish and leave. The SF relationship ensures there is no gap between the shifts, maintaining continuous operation in the factory.
Example 2: Server Switchover in IT
- Predecessor Activity: Start the new server.
- Successor Activity: Shut down the old server.
In an IT server migration process, the old server cannot be shut down (finish) until the new server has been started and is fully operational. This ensures there’s no downtime between the old and new servers, maintaining continuity of service.
Example 3: Security Guard Shift
- Predecessor Activity: Start the second guard shift.
- Successor Activity: Finish the first guard shift.
In a 24-hour security watch, the first shift can only finish when the second guard shift has started. This ensures that there is no lapse in security coverage during the handover.
Using SF Relationship in Primavera P6
To implement the Start-to-Finish (SF) relationship in Primavera P6, you follow these steps:
- Define Activities: Make sure both predecessor and successor activities are defined.
- Assign SF Relationship: In the Activity Details window, under the Relationships tab, assign the Start-to-Finish (SF) dependency to the successor activity, linking it to the predecessor activity.
- Adjust with Lag or Lead (Optional): You can introduce lag or lead if you want to adjust the timing of when the successor finishes relative to the predecessor starting.
Lag and Lead in SF Relationship
- Lag: Lag introduces a delay between the start of the predecessor and the finish of the successor. For example, if there is a 2-hour lag, the day shift might end 2 hours after the night shift starts to provide overlap during the handover period. Example: In a shift change, there might be a 30-minute lag to allow for debriefing between the incoming and outgoing shift workers before the day shift officially finishes.
- Lead: A lead (negative lag) allows the successor activity to finish slightly before the predecessor activity starts. Example: In a hospital setting, a day nurse might finish their shift 10 minutes before the night nurse starts, as long as essential handover tasks are completed in advance.
Advantages of SF Relationship
- Ensures Continuity: SF relationships are ideal in scenarios where continuous operations are required, such as in shift work, IT systems, or 24-hour services, ensuring that there is no gap between activities.
- Useful for Handover Processes: SF relationships are particularly effective in managing handovers between different teams, shifts, or systems where one process needs to keep running until another is ready to take over.
- Prevents Unwanted Early Finishing: It ensures that an activity doesn’t finish too early, which might lead to operational gaps, particularly in environments requiring continuous monitoring or service.
Limitations of SF Relationship
- Less Intuitive: The SF relationship is not as straightforward as FS, SS, or FF relationships. It can be confusing to set up and manage since it is not commonly used.
- Rarely Used in Standard Projects: Most projects don’t require this type of relationship. It’s mainly applicable in specific industries or situations that require uninterrupted transitions.
- Can Be Complex to Coordinate: Managing lag and lead times effectively in SF relationships can be challenging, particularly when coordinating between different teams or systems.
Real-Life Scenario of SF Relationship
Example: IT System Maintenance
Consider a scenario where an IT company is migrating data from an old system to a new one:
- Predecessor Activity: Start running the new backup system.
- Successor Activity: Finish the old backup system.
The old backup system cannot be taken offline until the new one is running and verified. This ensures data protection and continuity during the migration process. Using the Start-to-Finish relationship ensures there’s no downtime between shutting off the old system and starting the new one, minimizing risk.
When to Use SF Relationship
- Shift Transitions: When one shift or team needs to continue working until the next one has started, such as in factories, hospitals, or security teams.
- System Switchovers: When transitioning from one system to another, ensuring that the old system remains operational until the new system is up and running.
- Service Continuity: In processes where continuity is critical, and an activity must keep running until another starts to maintain service levels without interruption.
Conclusion
The Start-to-Finish (SF) relationship is an uncommon but valuable tool in Primavera P6. It is used in situations that require the completion of one activity to be dependent on the start of another, typically for tasks like shift changes, handovers, or system switchovers. While it is not as intuitive or widely used as other relationships like Finish-to-Start (FS) or Start-to-Start (SS), it plays a crucial role in ensuring continuity in operations where activities need to seamlessly transition without gaps. Proper management of SF relationships, with appropriate use of lag and lead, ensures smooth workflows in these specific scenarios.
