Two popular strategies are Shell Conversion and Mix and Match approach when moving from your old SAP ERP system to SAP S/4HANA. Both have distinct advantages based on the needs of your business, but choosing the best course of action requires knowing how they differ.  

Let’s examine each strategy in detail and assist you in selecting the one that best suits your requirements.
 

What’s Shell Conversion Approach? 

The Shell Conversion Approach focuses on transitioning from your existing SAP ERP system to SAP S/4HANA by first removing all data from the system, leaving only the configuration settings in place. This method offers more flexibility for customization than the standard system conversion approach. The steps involved are as follows: 

• Creating the Shell: The process begins by creating a “shell” of your current SAP ERP system, which means the system will be empty, containing only configuration settings and no transactional or master data. 

• System Configuration: The empty system will only include the necessary customizations and repository items. This system will then undergo the standard SAP S/4HANA system conversion process. 

• Flexibility for Adjustments: Since there is no data in the system, you have the flexibility to make any adjustments or configurations required for the new SAP S/4HANA system. 

• Data Duplication: Once the setup adjustments are complete, the system can be duplicated for the migration phase. 

• Data Migration: In areas where no significant changes were made to the configuration, migrating the data is straightforward. The data will be transferred at the table level, and any required changes to fit the SAP S/4HANA architecture will be handled by specialized afterburner scripts—similar to what happens in a standard system conversion. 

• Migration of Modified Areas: For parts of the system requiring major changes, the migration will be performed via secure system interfaces, ensuring that no historical records are transferred for those sections. 

This approach allows for a clean, customizable transition to SAP S/4HANA while ensuring that any necessary changes are implemented smoothly during the migration process. 

 

What’s Mix and Match Approach? 

The Mix and Match Approach is designed for organizations that want to move to SAP S/4HANA but wish to retain certain elements of their existing SAP ERP system, especially when the legacy system’s business processes or enhancements in ECC 6.0 are not fully suitable for a direct conversion. This approach accelerates the migration while keeping the best of the existing system. 

Here’s how the Mix and Match Approach works: 

• Starting with a Clean S/4HANA System: Unlike the Shell Conversion Approach, the Mix and Match approach bypasses the Shell Conversion phase and begins with a clean SAP S/4HANA environment, essentially taking the Greenfield route. 

• Using Reference Systems: While it starts with a new system, the transition is faster because it incorporates reference systems such as older ECC 6.0 setups, SAP Model Company systems, and Best Practice information. These reference systems help to speed up the process of setting up business processes by using expert-driven guidance. 

• Selective Retention: The key feature of this approach is selectively retaining parts of the existing SAP ERP system that have already met both current and future requirements. These areas of the solution will be preserved while the rest of the system undergoes a complete transformation. 

• Identifying Existing Issues: Before migrating, it’s crucial to identify and resolve any existing bugs or issues in the current system. Failing to do this step could lead to incomplete processes or siloed operations, which would jeopardize the entire transition to S/4HANA. 

• Customization and Automation Options: After identifying the areas that need to be retained, organizations have two options: 

• Manual Configuration: Engage experienced consultants to manually configure the existing solution into the new S/4HANA setup. 

• Automation Tools: Leverage available automation tools to streamline and facilitate the transition to SAP S/4HANA. 

This approach is less common than the Shell Conversion method but is valuable when you want to keep parts of your existing setup while benefiting from the flexibility and new features of S/4HANA. The Mix and Match approach allows for a more gradual yet optimized transition to the new system while protecting well-established and working components of the legacy environment. 

 

Factors to Consider in Choosing the Right Approach 

The migration strategy is greatly impacted by the quantity and complexity of your legacy data. A Brownfield (system conversion) strategy, which keeps a much of your current data and setups, might be advantageous for a larger, more complicated dataset. If a total revamp is required, a Greenfield (new implementation) method could be more suitable.​

The Brownfield technique is usually the most economical and expedient for businesses with limited resources or those looking for a faster move. This could, however, result in a loss of flexibility or the introduction of legacy inefficiencies. The Greenfield or Shell Conversion methodologies might provide a more streamlined, personalized transition if you are willing to devote more time and resources.​

If you wish to implement new S/4HANA processes or technologies while retaining some aspects of your current system, the Mix and Match technique can be helpful. This strategy enables a hybrid solution that makes use of current advantages while adjusting to the new platform.​  

 

Conclusion 

In conclusion, your business needs and the degree of change needed will determine which SAP S/4HANA migration strategy is best for you. The Shell Conversion technique is a great option if you want to re-engineer processes in specific areas without completely redesigning the system because it offers flexibility while keeping important elements of your current solution.  

However, the Mix & Match approach may be more advantageous if substantial adjustments to systems and procedures are required. This tactic keeps the tried-and-true components of your legacy system while combining the benefits of starting over.  

 

 

FAQ’s 

1. What’s the difference between Shell Conversion and Mix and Match approach? 

Shell Conversion removes all data, retaining only configurations for flexible migration, while Mix & Match keeps some existing system elements during the transition to SAP S/4HANA. 

2. Which approach suits complex legacy data? 

Shell Conversion is ideal for businesses with complex data, offering customization and flexibility during migration. 

3. Can I retain parts of my old system in Shell Conversion? 

No, Shell Conversion removes all data, allowing only configurations to remain for adjustments during migration. 

4. What are the benefits of the Mix & Match approach? 

Mix & Match lets businesses retain key elements of their old system while adopting new SAP S/4HANA features, offering a gradual transition.