Safety Stock Optimization Infeasibility Diagnosis options

You select which of the various constraints should be analyzed during infeasibility diagnosis:

• Minimum Service Time – Select this option to assess the minimum service time constraints in the model. If a minimum service time constraint is triggering infeasibility, the Constraint Name in the Inventory Constraint Summary table is “Min service time”. The Input Constraint indicates the current minimum service time and the Suggested Constraint indicates a value that can overcome the infeasibility. To set this option in a scenario item, select the “Minimum Service Time” field in the Inventory Optimization Options table and select "Yes" as the value.
• Maximum Service Time – Select this option to assess the maximum service time constraints in the model. If a maximum service time constraint is triggering infeasibility, the Constraint Name in the Inventory Constraint Summary table is “Max service time”. The Input Constraint indicates the current maximum service time and the Suggested Constraint indicates a value that can overcome the infeasibility. To set this option in a scenario item, select the “Maximum Service Time” field in the Inventory Optimization Options table and select "Yes" as the value.
• Maximum Safety Stock – Select this option to assess the maximum safety stock constraints in the model. If a maximum safety stock constraint is triggering infeasibility, the Constraint Name in the Inventory Constraint Summary table is “Max safety stock (DOS)” if the Safety Stock Basis is "DOS" or “Max safety stock (Quantity)” if the Safety Stock Basis is "Quantity". The Input Constraint indicates the current maximum safety stock and the Suggested Constraint indicates a value that can overcome the infeasibility. To set this option in a scenario item, select the “Maximum Safety Stock” field in the Inventory Optimization Options table and select "Yes" as the value.
• Non-Stocking Site – Select this option to assess whether or not setting the Stocking Site value in Inventory Policies to "No" is a cause for infeasibility. If a non-stocking site is a cause for infeasibility, the Constraint Name in the Inventory Constraint Summary table will be “Non-stocking site”, the Input Constraint is “NonStocking” and the Suggested Constraint is “Stocking”. To set this option in a scenario item, select the “Non-Stocking Site” field in the Inventory Optimization Options table and select "Yes" as the value.

If you do not check an option, these constraints are considered hard constraints.

In many cases, the constraints that causes infeasibility in Safety Stock Optimization are related and conflict with each other. For example, a customer-facing site is non-stocking, and it does not achieve the service time to the customer. In this case, you can either change the site to be stocking, or increase the required service time to make it feasible. Using the infeasibility options listed above, you choose which constraints to relax. When you select the checkbox for a specific constraint, it means you are willing to change the corresponding constraint to make the model feasible.

Coupa recommends that you run infeasibility diagnosis with all options checked in the first run. In this way, you can review the Inventory Constraint Summary table to identify what is causing the infeasibility. You can then determine which constraint(s) to relax in subsequent runs of infeasibility diagnosis. This analysis requires some knowledge of the guaranteed service time model.

Typically, if a non-stocking site constraint is causing the infeasibility, you should adjust the site to allow stocking.