Explanation of the Optimization Results 

Use

Optimization-based planning in Supply Network Planning (SNP) pursues a global solution approach by considering all restrictions and costs simultaneously and across the entire model. It therefore frequently finds a better solution than is possible with other planning methods. However, the results of the optimization run are not always easy to understand.

You can use the explanation tool to have the system explain two significant exceptional situations of an optimization run:

·        Non-delivery

·        Shortfall of safety stock

This function shows you the possible causes for the exceptional situations in the optimization run log. You can use the causes shown to check whether you can solve the problem by increasing capacities or extending horizons, for example. The system also suggests additional orders that you could use to remedy the missing quantities.

Among other things, you can specify the location products for which you want the explanation, and how detailed it should be.

Prerequisites

·        You have executed an optimization run and created a log for this run (that is, you have set the Write All Log Data indicator in the SNP or deployment optimizer profile). The explanation tool refers to the result of the optimization run as you see it in the log.

·        Between the optimization run and explanation run, you have not changed the SNP or deployment optimizer profile you used for the optimization run. You have also not changed the optimization-relevant settings in planning version management.

·        In the case of a deployment optimization run, you have chosen an optimal cost allocation. The explanation tool does not support fair share or push distribution.

Features

Non-deliveries and lack of safety stock can have the following five causes:

·        Capacity Constraints

·        Time-Based Constraints and Maximum Lot Sizes

·        Product Availability

·        Lead Time

·        Costs

The explanation tool displays these causes, but does not explain why the optimizer fulfills the demand of one product but not of another when there is a lack of capacity.

Capacity Constraints

In the SNP or deployment optimizer profile, you have defined that the optimizer is to consider certain capacity constraints. The optimizer considers the resource capacity defined in the resource master data.

A possible cause for non-deliveries is that the system cannot fulfill the demand with the available resource capacity.

The system shows you the following data of the capacity problem:

·        Resource with the capacity problem.

·        Number of the period (bucket) where the capacity problem occurs.

·        Missing capacity of the resource.

If your planning buckets profile also includes daily periods, the system cannot determine any capacity problems caused by calendar problems within the time frame covered by daily periods. For example, the system cannot suggest capacity could be made up by working on a holiday.

Time-Based Constraints and Maximum Lot Sizes

In interactive SNP planning, you have defined time-based constraints (upper limits) for the capacity of specific sources of supply (such as for production or transportation). For more information, see Definition of Time-Based Constraints in Interactive Planning. In the SNP or deployment optimizer profile, you have also or alternatively defined that the optimizer is to consider maximum lot sizes.

The system displays the following data:

·        Name of the source of supply for which you have set the upper limit or maximum lot size.

·        Name of the product for which you have set the upper limit or maximum lot size.

·        Procurement type of the location product (in-house production, external procurement, and so on).

·        Number of the period where the capacity problem occurs.

·        Quantity by which you must raise the upper limit to solve the problem. In the case of the production upper limit, the system does not show the quantity but rather the number of executions of the production model (PPM) or production data structure (PDS). An execution of the PPM or PDS corresponds to the output quantity you specified in the PPM/PDS.

Product Availability

A possible cause for non-delivery can be that products are not available because a source of supply does not exist (for example, because the bill of material has not been completely defined).

The system shows you the following data of the product availability:

·        Name of the product and location

·        Number of the period in which the product quantity is missing

·        Missing quantity of the product

The system does not check the validity of PPMs/PDSs or transportation lanes. It also does not check the validity of time-dependent parameters of PPMs/PDS (such as material consumption).

If you have defined a PPM/PDS that is not valid until the middle of the planning horizon, for example, the system does not determine any availability problems in the first half of the planning horizon.

Lead Time

Due to a long duration of shipment and production, the lead time it takes for a product to be available in a specific period can stretch over several periods. The system therefore frequently cannot fulfill demands because the lead time stretches into the production or stock transfer horizon, or the planned delivery time. The lead time can even stretch back into the past (before the planning period).

The system shows you the following data of the lead time:

·        Name of the product and location

·        Name of the source of supply

·        Procurement type of the location product

If the lead time stretches into the past, the procurement type is S (initial stock level).

·        Missing quantity of the product

·        Start and finish time of the order

·        Number of days by which the corresponding horizon (production or stock transfer horizon) or the planned delivery time has been violated.

Costs

The fulfillment of the demand and the safety stock requirement is called a soft constraint for the SNP or deployment optimizer. That means there are penalty costs for not fulfilling the demand. If you have set the penalty costs for non-delivery and safety stock shortfall too low in the location product master data, the optimizer may decide not to fulfill the demand. This may be the case if the total costs are lower when demand is not fulfilled.

The system displays this possible cause in a message.

If you have not defined penalty costs for safety stock shortfall, the optimizer cannot determine the cause. If you run a model consistency check, you will, however, see a corresponding message.

Order Suggestions

The system suggests additional orders that you could use to remedy the missing quantities.

If you use the suggested orders or try to solve the exceptional situations another way depending on the displayed causes, a new optimization run can however still lead to similar or different problems due to the dependencies.

For example, if you increase the capacity of a resource to remedy the missing quantities of a specific product, the system can use the additional capacity to cover the missing quantities of another product with higher priority.

Further Information

The explanation tool only generates one possible explanation for each exceptional situation. However, there may be other explanations as well. For example, if the system finds a capacity bottle-neck for a resource and suggests increasing the capacity of this resource, another solution might be to increase the capacity of an alternative resource.

If the results of the explanation tool are incorrect, this might be because the optimization solution on which they are based was not optimal (for example, due to runtime restrictions).

Activities

To execute the explanation tool, from the SAP Easy Access screen, choose Advanced Planning and Optimization → Supply Network Planning → Reporting → Optimizer Log Data. Then select an optimization run and choose Explain. The Explanations of the SNP Optimization Results screen appears. Here you make settings such as the target and level of detail of the explanation, and choose Execute. For more information, see Configuration of the Explanation Tool.

After you have executed the explanation run, you see the Optimization Run X screen that displays the logs for the selected optimization run. The tree structure contains the entry Explanations with the subentries Configuration and Explanation Results. If you double-click on these entries, you see your entry data and/or the results of the explanation run on tab pages on the right side of the screen. If the upper table on the right side of the screen contains several entries, you can double-click on an entry in the lower table to see its detailed data.

You can also execute the explanation tool from the Optimization Run X screen by choosing Explain.

If you want to execute the explanation tool in the background, choose Advanced Planning and Optimization → Supply Network Planning → Reporting → Explanation of Optimization Results.