System conversion is a transition scenario that existing SAP ERP customers can opt to apply to convert their existing SAP ERP solution to SAP S/4HANA. This includes retaining their business data, custom development, and configuration. Customers choosing this scenario may want to minimize change initially and then innovate selectively going forward.
In a system conversion scenario (while alternatives exist), it is highly likely that the customer will invest in new hardware to run the SAP S/4HANA application. This is due to factors like the database running in memory. Customers perform an initial sizing, and procure the new hardware based on the sizing results at the beginning of the project.
These are some of the primary steps performed when converting an existing SAP ERP system into a new SAP S/4HANA system.
The primary steps of a system conversion are:
Prepare ERP System: Clean up custom code and reduce data volumes
Database Migration: Move to SAP HANA database (only if source is on a DB other than HANA)
System Update: Provide new applications and tables
- Data Conversion: Convert table content to new data model.
- Software Configuration: Implement SAP S/4HANA mandatory and simplification items and reuse majority of existing processes
Software Update Manager (SUM) is the tool that facilitates the database migration, software update, and data conversion steps. The SUM creates a shadow repository on the target database. A shadow system consists of a shadow instance and a shadow repository.
Database Migration Option (DMO) is an optional feature of the Software Update Manager (SUM) tool. It combines three system conversion processes into a single step procedure: database migration + system update + data conversion.
System Move adds an additional step that facilitates migration to new data centers. The functionality reduces complexity, downtime, transition time, and costs of the system conversion by packaging multiple steps together and adding the system move to facilitate switching from the old servers to new servers in the target hyperscaler.
Lift and Shift Approach
Lift and Shift moves an entire system without change to a new landscape. For example:
From SAP S/4HANA On-Premise 2020 to SAP S/4HANA Cloud, private edition 2020.
The technical overview diagram displays a high-level view of the SUM (Software Update Manager) process. Software Update Manager is a tool used by the SAP Basis team to upgrade SAP on-premise software. This tool is also used in the system conversion scenario to upgrade the SAP ECC system to SAP S/4HANA.
There are other tools used in this process, which include:
SAP readiness check: Responsible for identifying which components need to be adjusted on SAP ECC in order to work on SAP S/4HANA
Maintenance planner: Responsible for calculating the upgrade path
DMO: Responsible for the Database Migration and Data Structure Conversion from any database to the SAP HANA database
The SUM process starts with the conversion of the existing SAP ERP Sandbox system. When starting the conversion, SUM will perform a series of checks on the Sandbox. After running the checks, SUM will fail and specify what components are not suitable for conversion. This list serves as baseline for the activities to be performed in order for the conversion to be completed successfully.
Once all SUM prerequisites are adjusted and/or adapted to work on SAP S/4HANA, the SUM process is started again and the sandbox system converted. This activity can be performed several times to the satisfaction of the project team. Once satisfied, the team will start the planning of converting the Development, Quality and Production systems.
DMO is available with Software Update Manager 1.0 SP09 and higher, and can be used for systems based on AS ABAP. It can be used for other target database types as well.
The processing sequence is based on the shadow system functionality of SUM. The SUM creates the shadow repository on the target database until downtime phase, while in parallel the SAP HANA database is setup (client, schema, and so on). Then the database connection of the SAP system is switched to the target database, and then the downtime starts. After migration of the application data (including data conversion), the upgrade is finalized and the SAP system runs on the target database. The source database continues to run and the application data in it is not modified, so it remains a fallback throughout, until the process is successfully completed.
For the transition from SAP ERP 6.0 to SAP S/4HANA, SAP provides information about the relevant changes that might have an impact, grouped by simplification items, from the simplification item catalog. The SAP Readiness Check provides the subset of the simplification items that may apply to your analyzed system.
The following area is covered by the SAP Readiness Check for SAP S/4HANA:
Add-Ons and Business Functions
SAP Add-ons and business functions as well as third party add-ons have to be checked for their compatibility with SAP S/4HANA
SAP software is listed and rated
Third party software is listed only
Custom Code and Development
Custom code analysis versus SAP S/4HANA compliance, based on SAP simplification database
SAP Readiness Check provides Bill of Materials (BOM) of affected objects as well as SAP Custom Development Projects (CDPs)
An in-depth custom code management activity to follow during project execution
Data Volume Management
Analysis of data volumes in sources system
Recommended SAP Fiori Apps
SAP Fiori deployment follows the same considerations as that for new implementation of SAP S/4HANA on-premise. This is an activity that the project team must take care of by following the high-level plan for the UX track in an implementation as shown here. SAP Fiori apps recommended based on the transaction usage history in the evaluated system will additionally help to determine the UX scope.
SAP S/4HANA Sizing
The SAP S/4HANA sizing check lets you run a sizing simulation and provides information about your sizing values and data volume management potential. To calculate the right target SAP S/4HANA system size, consider the initial target SAP S/4HANA size calculated from your current SAP ERP database size, future database growth, possible data volume reduction, and potential new functionalities.
The Simplification Item Check serves two purposes:
Relevance check: Determine which simplification items are relevant for the specific system in which you are running the simplification item check. This shall help you to assess the functional and technical impact of the system conversion on your system.
Consistency check: During the conversion process, your system will be migrated to the new data structures and new processes. The conversion routines rely on consistent data in the system in order for this to happen automatically. If the simplification item check identifies data inconsistencies or missing mandatory preparation activities which could cause the system conversion to fail, it will make you aware of these issues so you can correct or exempt them before the actual system conversion starts.
Simplification items check can be done and compared using the simplification database, which can be found in any SAP NetWeaver 7.5 system and above.
When performing a system conversion, new hardware is generally provisioned to support the SAP S/4HANA solution. This results in a temporary dual landscape (maintenance and project). The project landscape is an exact system copy of production (with data desensitized).
As the project team start their conversion activities, the maintenance team continue their business as usual changes through the maintenance environment. This means that every time a maintenance change goes through the maintenance landscape, the project landscape is now out of sync. We use Retrofit to keep the project environment in sync with the maintenance landscape. Retrofit copies the change into the project landscape to keep the environments in sync.