Understanding Transportation Lanes Issues and the SNP Heuristic

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Executive Summary

SNP heuristic will stop with incorrect transportation lanes.
We cover the low-level code in the SNP heuristic.
We provide a recommendation for how to manage transportation lanes and SNP heuristics.

Introduction to Transportation Lanes

Transportation lanes connect the supply network locations, and they have a huge number of APO settings. You will learn the critical characteristics of the transportation lanes.

Setting Up Transportation Lanes Correctly

When Transportation Lanes are not correctly set up, they will typically stop the SNP Heuristic from running. What follows are the steps for determining issues with the Transportation Lanes for the SNP Heuristic.

Step 1: Run the Low Level Code transaction in SAP APO (/SAPAPO/SNPLLC). When problematic Transportation Lane errors exist in the system, these errors will show in this transaction. The errors identify the locations and material number, which stopped the SNP Heuristic from running.
Step 2: Using this information from SNPLLC, the APO resource can then go to the Transportation Lane transaction (/SAPAPO/TL1) and block the Transportation Lane.
Step 3: Re-Run the Low Level Code transaction to see if the error persists.
Step 4: If there are no errors from Step 3, rerun the SNP Heuristic.

The Issue of the Low-Level Code

This issue has come to be known as the Low Level Code Issue. It is more properly considered an issue with incorrect Transportation Lanes being set up in the SNP planners system. Or in some cases, with Transportation Lanes that have non-overlapping validity dates placing the SNP Heuristic into a loop, which will stop the SNP Heuristic planning run, requiring intervention and troubleshooting by an IT resource. The following scenarios have been explained as reasons for the Low Level Code error.

Circular Transportation Lane Relationships: This is where an extra Transportation Lane is created to create the Transportation Lanes in multiple directions between two or more Locations.
1. Example 1: Where Transportation Lanes are going in both directions between two Locations.
2. Example 2: Where there are Transportation Lanes are created in a circuit, one from Location A or Location B, from Location B to Location C, and then from Location C to Location A.
Subcontract Transportation Lanes Setup Incorrectly.
Transportation Lanes with Correct and Non-Overlapping Validity Periods: This is the one scenario where the flaw is clearly within SNP. SNP is designed to accept any number of Transportation Lanes between Locations or any other setup as long as the validity periods do not overlap. This allows the supply network to be flexibly altered through time and for Transportation Lanes to be set up within APO before their need date but automatically activated as time passes. However, scenarios have been found where Low Level Code errors are found even when the validity periods do not overlap.

Improving Transportation Lane Input

While it would be convenient if the SNP Heuristic were designed to skip problematic Transportation Lane combinations, this would seem to be an issue that could be managed by improving Transportation Lanes’ input by those that add Transportation Lanes.

Circular Transportation Lane Relationships: The Transportation Lane transaction in SAP APO makes it quite easy to create Transportation Lanes in the wrong direction. The incidence of this should be able to be reduced through documentation and explanation to SNP planners.
Subcontract Transportation Lanes Setup Incorrectly: Subcontracting, as well as subcontract Transportation Lanes, are confusing – and another area that could be documented and explained for SNP planners.
Transportation Lanes with Correct Validity Periods: This is a genuine flaw for which an OSS note exists. However, a workaround for this issue may be to block Transportation Lanes until it is time to activate them. This would allow those that update and Transportation Lanes to add Transportation Lanes in advance of their actual need. It would also require the updates to keep a calendar of when the new Transportation Lanes are activated, unblock them, and then block other Transportation Lanes that would interfere with the new Transportation Lanes.

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Conclusion

While one might say that the SNP Heuristic should be able to skip problematic parts of the supply network, in practice, the SNP Heuristic does not work this way. The Low Level Code is a mechanism of segmenting the supply-planning problem into a sequence (more generally known as problem decomposition) because the heuristic can only process a tiny part of the supply-planning problem at a time. The term “code” represents a priority value of combining factors that make up a sub-problem (such as a particular product and location).

It is enlightening to review the functionality/control provided by SAP in this area. The extent of control provided by SAP concerning how the supply network problem is processed is to run the SNP Heuristic to the BOM level. The SNP (location) Heuristic could be run for just finished goods, but not semi-finished or raw materials. Therefore SAP allows for sub-segments of the problem to be run. For instance, to create a master production schedule run rather than a general or initial supply planning run.

But that is all very simple compared to the logic required to provide the ability to circumvent problematic portions by responding to errors within the run.

Nothing in SCM 7.0 to Address This Issue

I reviewed the available enhancement packs available for SAP SCM 7.0 and was not able to find anything related to the improvement of the SNP Heuristic, much less the specific issue related to Transportation Lanes. As for the issue with Transportation Lanes with non-overlapping validity periods that share Locations that cause contention, there is the potential that SAP will fix this issue. But I would say the likelihood is low.

Recommendation

The best option available for most companies is to improve the quality of Transportation Lanes. This can be accomplished with documentation and some time spent explaining how to keep the Transportation Lanes created at a higher quality level.