The Actual Working of Relationships in Primavera P6 Beyond FS, SS, FF, SF

Relationships define how activities are related to each other in project schedule logic. Activity sequence, float values, and critical path are calculated by Primavera P6 using relationships. A schedule becomes reliable only when the relationship logic goes right. Most of the users learning Primavera P6 Training understand the basic four relationship types, but the actual technical process which happens with these is a lot more detailed.

Not all relationships are treated equally by Primavera P6 when it comes to scheduling. The direction of the logic, calendar rules, the influence of lag, and the impact of duration are all assessed by the software before placing an activity on the timeline.

How Primavera P6 Evaluates Relationship Logic While Scheduling?

For every relationship, Primavera P6 performs three major scheduling checks:

• Forward pass to find the earliest dates
• Backward pass to find latest dates and float
• Logic to enforce which relationship is controlling

It is not final because the relationship logic links the activities. Primavera P6 checks:

• Activity durations
• Calendars of both activities
• Any calendar of relations, if applied
• Lags or leads used
• Delay impact on successor
• Constraint priority if present

Considering all these points, Primavera P6 decides which relationship becomes driving logic. Only the driving relationship controls the start or finish date of the successor while other links still exist but remain non-driving.

That is to say, visible links do not always show true scheduling control, and technical users must track the driving logic every time a schedule is updated.

Relationship Types and Their True Internal Behavior

Most of the planners know just simple definitions of FS, SS, FF & SF. But Primavera P6 treats these relationship types with deeper calculation. Below table explains the processing difference:

Technical points:

• FS becomes the default driving logic in most of the cases.
• SS and FF mostly rely on the usage of lag.
• SF can drive finish logic even when rarely used.

P6 selects the relationship that creates the most restricted scheduling sequence. That restricted link becomes the driving relationship.

This internal logic in the execution of projects is important; the point is that changes in durations or calendars can switch which relationship becomes driving.

Lag, Lead and Calendar Influence in Relationship Logic

Lag is the extra time between related activities. Lead, or negative lag, is a decrease in waiting time between them. Primavera P6 handles lag as a technical value related to calendars.

Technical processing rule:

• Lag always follows the predecessor calendar
• If a relationship calendar is applied, it overrides both activity calendars.
• Lead compressesthe schedule but can reduce float and produces false urgency.

Schedulers should avoid random lead usage because when calendars shift, it may lead to sudden float loss. Primavera P6 still computes it correctly; however, project control now becomes more sensitive to small changes.

Construction and infrastructure work are increasing in Noida. Hence, fast schedules with overlapped activities and complex lag design are in demand. Professionals who complete Primavera P6 Training in Noida should, therefore, understand how lag affects float and critical path in fast-track execution.

Driving Relationships, Float Path, and Logic Overload

Driving relationships forces the successor to start or finish. The driving logic is highlighted in Primavera P6 Gantt Chart. Having many relationships is not a problem, but at any one moment, there is only one driving relationship for that activity.

Driving logic determination depends on:

• Restrictive calendar alignment
• Lag pushes dates further.
• Constraints variable schedule decisions
• Duration changes introducing new restrictions
• Out-of-sequence progress

Float analysis is also directly controlled by driving logic. That’s why float paths must be traced in order to detect real risk. Often, Primavera’s Longest Path method is superior at revealing risk than simply checking critical path flags.

Most large EPC and infrastructure companies in Delhi require the teams to demonstrate float path traceability in support of schedule claims and progress validation. It is because of this accountability-driven scheduling environment that the learners of the Primavera P6 Training Institute in Delhi give enormous emphasis on float path analysis and driving logic tracking. The scheduling trend in the city is based on full control over dependency behaviors.

Constraints, Calendar Exceptions and Interruptible Logic

Constraints refine how relationships work. When a constraint is applied, Primavera P6 often gives less weight to the driving relationship and favors the constraint.

Important effects:

• Start On can override FS control
• Must Finish By changes backward pass and changes total float
• Activity Non-Interruptible forces continuous work without gap
• Calendar exceptions can unexpectedly switch driving control

The following changes do not break the logic, but they change the decision order that Primavera uses. Technical planning teams should continuously review:

• Driving relationship shifts
• Constraint drive on float
• Whether non-critical activities become critical suddenly due to new restrictions

This review is essential to avoid an unnoticed change from becoming a big execution problem.

Sum up,

Relationship logic in Primavera P6 goes way beyond linking. Utilizing a rather involved technical process, the software decides which relationship becomes controlling. It looks into calendars, lag, durations, and constraints in order to derive real scheduling behavior.

This is subject to variation with every schedule update. For those users who monitor just FS, SS, FF, and SF without understanding internal logic, their schedules may appear to be correct but misbehave during execution.