What-If Modeling
What If Modeling is a process that allows planners to recognize changes to stocking plans and budget the impact from events and changing assumptions. With proper utilization, businesses can make more informed decisions and predict the impact of those decisions more accurately.
When only comparing scenario results, you can change and compare scenario properties like:
• Inventory assumptions
• External scenario inputs
• Set-level parameters
When using What-If Modeling, you can go one step further in analysis by altering foundational part‑level modeling properties like:
• Resupply hierarchy
• Forecast modifiers
• Service group constraints
• Segmented parameter overrides
This table shows the capabilities of Comparison Scenarios versus What-If Modeling:
|
Modeling Input / Change Type
|
Comparison Scenarios
|
What‑If Model
|
|---|---|---|
|
Compare stock levels, external scenario settings, optimization parameters
|
 This is the primary usage of Comparison Scenarios. For example, changing fixed inventory and evaluating it against the production ROP. |
 Stock level comparisons are not supported. |
|
Change availability service group hierarchies
|
Achieve this by changing the service group hierarchy directly and then recalculate the Comparison Scenarios to pull in the modified service group hierarchy data. |
Service group hierarchy comparisons are not supported. |
|
Run reporting comparisons like Scenario Summary, or Budget Reports
|
This is also a primary usage of Comparison Scenarios. |
The reporting comparisons use the scenario copies, but the what-if model influences the Comparison Scenario results. |
|
Make forecast adjustments applied at a model level
|
Achieve this by modifying the scenario settings. However, the output it is not reusable or segment-scoped. |
Achieve this by using the What-If Model, and the output is reusable and can be segment-scoped. For example, set the model to have a +5% forecast for a segment. |
|
Change the resupply hierarchy to test alternate location relationships
|
A Comparison Scenario cannot override the resupply hierarchy without making changes to the production data. |
Achieve this by modifying the hierarchy without changing the production data. |
|
Change the part‑level modeling inputs, such as structural or master data related
|
Part‑level overrides are not supported. |
Achieve this by changing the part-level inputs on the model for selected SKUs only. |
|
Apply changes to selected SKUs
|
Selective SKU-scoping is not supported. A Comparison Scenario applies to the entire scenario population. |
This is a primary usage of What-If Models. Achieve this by applying the model only to SKUs in an assigned segment. |
|
Test operational or structural changes without altering production data
|
Production master data is updated with a Comparison Scenario. |
This is also a primary usage of What-If Models. |
|
Reuse the same changes across multiple scenarios consistently
|
Manually intensive to keep each Comparison Scenario aligned. |
A What-If Model can be attached to many scenarios to ensure consistent inputs. |
|
Experiment with hierarchy changes before adopting in production
|
A Comparison Scenario cannot isolate hierarchy experimentation outside of production. |
This is also a primary usage of What-If Models. Hierarchy changes should not be made production until validated. |
Collaboration Using What-If Models (What-If Modeling Workflow)
A What‑If Model is never run by itself, instead, it is the input to a Scenario that gets calculated and produces the results. Review these key concepts and prerequisites before getting started with using the What-If Modeling Workflow:
Key Concepts
|
Comparison Scenarios
|
These are the scenarios created by copying the Baseline Scenario and modifying selected inputs. Each Comparison Scenario can be calculated with an assigned What‑If Model, producing results that can be evaluated side‑by‑side to understand the impact of those modeling changes.
|
|
Segments
|
These will define the SKU population affected by the What-If Model.
|
|
Resupply Hierarchy
|
This is the relationship structure that will be used to propagate demand and calculate the pipeline forecasts.
|
|
Availability Service Groups
|
These will control which hierarchy is used during the Optimization process.
|
Prerequisites
◦ Access to Inventory Optimization in Servigistics
◦ Required permissions to create Scenarios and Segments
◦ Understanding of Part Hierarchies and Service Groups
The What-If Modeling Workflow
Follow these instructions:
1. Identify the scenario that will be used as the Baseline Scenario.
2. Identify the segment that includes the SKUs for your comparison.
 |
If you have to create or modify the segment, then you will need to run the Synchronize Database AutoPilot process before proceeding to the next step.
|
3. Create a Service Group for reporting on the Business Unit
▪ Do not set any targets
▪ Assign the segment identified in step 2.
Add the Service Group created in step 3 to this newly copied Optimization Set.
5. Define the What-If Model using the What-If Modeling page.
▪ Assign the segment identified in step 2.
▪ Define the modeling properties in the Details section for the What-If Model.
6. Create Comparison Scenarios by making one or more copies of your baseline Scenario using the Copy process on the Scenarios page.
▪ Assign the What-If Model defined in step 5.
▪ Make adjustments to the scenario parameters.
|
|
The number of copies you make depends on the number of comparisons you plan to review. If you have three possibilities to explore then create three copies — one for each possibility.
|
7. Run the Calculate process for each Comparison Scenario on the Scenarios page.
8. Review the outputs:
a. Open the Scenario Summary page to view the output of the Comparison Scenarios.
b. Open the Scenario Budget Summary page to compare the results.
c. Open the Service Group Budget Summary page to compare the results.
Example
There may be times when it would be helpful to see the impact of changes to the inputs to Inventory Optimization for a Business Unit. For example, this workflow considers three Comparison Scenarios that are modified copies of the same Baseline Scenario, utilizing both Scenario Comparison (evaluating external values) and What-If Modeling (evaluating foundational forecasting):
Scenario 1
5% forecast increase with current inventory
Scenario 2
5% forecast increase with optimized stock levels
Scenario 3
5% forecast increase with current recommended stock levels
Follow the recommended workflow instructions:
1. Identify the Baseline Scenario.
2. Identify the Segment that contains the SKU.
3. Create a Service Group and assign the Segment that contains the SKU. Do not assign any targets.
4. Create a copy of the Optimization Set that is assigned to the Baseline Scenario and assign the newly created Service Group.
5. Create the What-If Model with these specifications:
Details
▪ Field = Customer Period Forecast
▪ Adjustment Operation = Increase by Percent
▪ Value = 5
Assigned Segments
The segment identified in step 2.
6. Create 3 copies of the Baseline Scenario with these specifications:
Scenario 1 – 5% Increase with Current Inventory
▪ Optimization Set = The copy of the Optimization Set defined in step 4
▪ What-If Model = The What-If Model defined in step 5
▪ Use External Values = Use Inventory Position
Scenario 2– 5% Increase with Optimized Stock Levels
▪ Optimization Set = The copy of the Optimization Set defined in step 4
▪ What-If Model = The What-If Model defined in step 5
▪ Use External Values = None
Scenario 3– 5% Increase with Current Recommended Stock Levels
▪ Optimization Set = The copy of the Optimization Set defined in step 4
▪ What-If Model = The What-If Model defined in step 5
▪ Use External Values = Use Production ROP
7. Calculate the 3 Comparison Scenarios.
8. Review the output.