Introduction:
In Critical Path Method (CPM) scheduling, managing out-of-sequence activities is crucial. Planera provides two primary options to handle such scenarios:
Retained Logic
Progress Override
🔄 Retained Logic
Definition:
Retained Logic ensures that the original network logic is preserved. If an activity starts before its predecessor finishes (out-of-sequence), the remaining work is delayed until the predecessor completes.
Key Characteristics:
Adherence to Original Plan: Maintains the integrity of the initial schedule logic.
Delay in Remaining Work: Prevents continuation of the successor activity until the predecessor is complete.
Accurate Critical Path: Ensures the critical path reflects true project dependencies.
When to Use:
Projects where maintaining the original sequence is vital.
Scenarios where out-of-sequence work could lead to quality or coordination issues.
Example:
If Activity B is scheduled to start after Activity A finishes, but B starts early, Retained Logic will pause B’s remaining work until A is complete.
🚀 Progress Override
Definition:
Progress Override allows the schedule to ignore the original logic ties for out-of-sequence activities, letting them continue without waiting for predecessors.
Key Characteristics:
Flexibility: Accommodates real-world deviations from the plan.
Potential Logic Conflicts: May result in unrealistic float values or misrepresented critical paths.
Resource Challenges: Can lead to resource overallocation if not managed carefully.
When to Use:
Projects requiring flexibility due to frequent changes.
Situations where activities are independent despite scheduled dependencies.
Example:
Using the earlier scenario, if Activity B starts before Activity A finishes, Progress Override lets B continue without interruption, regardless of A’s status.
📊 Key Differences in CPM Behavior
Aspect | Retained Logic | Progress Override |
Out-of-sequence progress | Delays successor until predecessor finishes | Allows successor to continue |
Schedule realism | Conservative | Field-realistic |
Critical path behavior | Accurate to plan logic | May shift unexpectedly |
Float impact | Preserved | May become artificially inflated |
Best suited for | Claims, risk-controlled projects | Fast-moving or field-driven execution |
🎥 Simulation Example
Let’s say we have this simple chain of tasks:
ID | Task | Duration | Logic |
A | Excavate | 3 days | — |
B | Pour Footings | 2 days | FS after A |
C | Backfill | 1 day | FS after B |
🗓️ Planned Schedule
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 |----- A -----| |---- B ----| |-- C --|
Examples from Planera:
Scenario 1: Out-of-sequence completed activity:
Consider the following network. All activities are in chain.
Now B is completed out-of-sequence.
Results for Retained Logic:
Observe that C waits for B to finish, thereby respecting network logic.
Results for Progress Override:
Observe that C starts at Data Date, and thus breaking the planned network logic.
Scenario 2: Out-of-sequence In Progress activity:
Consider the following network. All activities are in chain.
Now B is progressed and has 0 remaining duration.
Results for Retained Logic:
Observe that C waits for B to finish, thereby respecting network logic. Since B has 0 remaining duration, therefore, C starts when A ends.
Results for Progress Override:
Observe that C waits starts at Data Date, and thus breaking the planned network logic.
⚖️ Summary Table
Risk | Retained Logic | Progress Override |
Logic breakage | Prevented | Possible |
Reflects field reality | ❌ | ✅ |
Claims and delay analysis | ✅ | ❌ |
Critical path risk | Low | High |
Float distortion | Minimal | Likely |
✅ Best Practice Tips
Use Retained Logic for projects with strict sequencing, risk exposure, or legal/contractual obligations.
Use Progress Override for agile field conditions or fast-moving execution — but monitor float and drift closely.
Always review Out-of-Sequence Logic Reports and consider hybrid strategies with manual overrides.