10    System Conversion

System conversion means converting an existing SAP ERP system into an SAP S/4HANA system. SAP offers many useful methods and functions to help you determine and implement the required adaptation tasks.

System conversion refers to a transition scenario in which you convert a single SAP ERP system into an SAP S/4HANA, on-premise, system. According to the vocabulary used in IT transformation projects, this scenario follows the so-called brownfield approach. In contrast to a new implementation of an SAP S/4HANA system (greenfield approach), your application data, configuration data, and custom developments are still available after the system conversion. The system conversion procedure is only available for the on-premise variant of SAP S/4HANA.

When you convert an SAP ERP system into an SAP S/4HANA system, you’re migrating to the SAP S/4HANA product family. You’ll change to the SAP HANA in-memory database (if you hadn’t already), and the simplifications of SAP S/4HANA are implemented (see Section 10.2). This chapter introduces the procedures and tools used for system conversions.

[»]  The “System Conversion” Concept

Because converting an existing SAP ERP system into an SAP S/4HANA system also involves a product change, this transition scenario is also referred to as a system conversion. We would not call it an “upgrade” because an upgrade would entail installing a new version of the same product.

10.1    Overview of the System Conversion Project

You’ll have to consider two aspects when converting your system: the technical procedure with which you will install the SAP S/4HANA software and the process of migrating to the new product, which involves changes to the functions and processes you know from SAP ERP already.

As shown in Figure 10.1, in addition to performing technical conversion steps, you’ll also have to adapt the functional scope of your data structure when migrating to SAP S/4HANA.

System Conversion to SAP S/4HANA: Technical Conversion and Adaptation Requirements

Figure 10.1    System Conversion to SAP S/4HANA: Technical Conversion and Adaptation Requirements

An example of a possible adaptation requirement is the credit management function, which we introduced in Chapter 1, Section 1.2.1. According to the principle of one, SAP S/4HANA supports only one credit management solution, which might require adaptation in some cases. Customers who use Credit and Risk Management (SD-BF-CM) in SAP ERP need to change to the new credit management function, SAP Credit Management (FIN-FSCM-CR), when migrating to SAP S/4HANA. However, SAP Credit Management is already available in SAP ERP so you can change to this solution before you convert your system. In addition to functional adaptations due to the different solution scope of SAP S/4HANA, the simplification of the data structures can also affect your custom developments.

Various methods and tools are available in the individual conversion project phases to help you determine what adaptation work you need to migrate to SAP S/4HANA:

You can use the Software Update Manager (SUM) to install SAP S/4HANA software during the system conversion and to install subsequent updates and upgrades. SUM provides options for reducing downtime during the migration project and is regularly updated via Software Logistics Toolsets (SL Toolsets). Section 10.2.7 explains how to use SUM.

[»]  Additional Information

Since June 2017, the SAP Readiness Check for SAP S/4HANA has been available. This cloud-based tool is available for free to anyone with a current SAP maintenance agreement. The readiness check reviews both your production (PRD) systems (or copies thereof) and your development (DEV) systems, determines their compatibility for SAP S/4HANA conversion, and provides the necessary conversion preparation steps. Among other results, the SAP Readiness Check for SAP S/4HANA displays the simplification items relevant to your specific SAP ERP 6.x system. Simplification items are identified according to factors such as transactions used and table contents.

More information (including the user guide and required configuration settings) can be found at https://help.sap.com/viewer/p/SAP_READINESS_CHECK.

10.1.1    System Conversion Process

Figure 10.2 illustrates the basic steps, as well as the relevant tools, you’ll need to perform to convert your system into an SAP S/4HANA system.

Tools Used for the System Conversion

Figure 10.2    Tools Used for the System Conversion

During the prepare and planning phase of the system conversion project, you’ll have to verify the system requirements. For example, SAP does not provide one-step system conversions for older SAP releases (for example, SAP R/3 Enterprise Edition 4.6C). You’ll also use the simplification list, the Maintenance Planner, prechecks, and the custom code migration worklist to obtain an overview of the required adaptation tasks during this phase. For example, you’ll have to determine the timeframe for implementing the new simplified processes and determine when you want to use the new SAP Fiori-based user interfaces and which SAP GUI transactions you want to continue to use after the system conversion.

The tools and functions for the prepare and planning phase are already available in your existing SAP ERP source system. Because you can implement numerous adaptations in this system (and some may need to be implemented before the conversion), you should perform the prepare and planning steps early in the conversion project.

In the adaptation and test phase (see Figure 10.3), you’ll convert your development system (see Section 10.1.2) and perform the planned adaptations. Tests (usually, several test runs are required) and end-user training are preparatory steps for the go-live.

In the execution phase, you’ll perform the technical SAP S/4HANA conversion using SUM. SUM combines three steps in one integrated process. In a one-step procedure, you’ll convert to the SAP HANA database, change the software, and convert the application data from your legacy data structure to the new data structure. When the SAP S/4HANA production system goes live, you can scale back the existing SAP Business Suite system landscape.

Figure 10.3 provides an overview of the individual tasks for the SAP S/4HANA conversion project phases.

Project Phase Tasks for the System Conversion

Figure 10.3    Project Phase Tasks for the System Conversion

Section 10.2 describes the individual conversion steps in detail.

[»]  Additional Information

The “Conversion Guide for SAP S/4HANA” provides basic information on the SAP S/4HANA system conversion process. Select your SAP S/4HANA version at https://help.sap.com/s4hana.

SAP Note 2332030 contains additional information on specific preparatory and follow-up steps for accounting.

10.1.2    System Group Conversion

The customer system landscape is a determining factor for the SAP S/4HANA system conversion. Usually, a system landscape consists of a group of several SAP ERP systems that are connected via transport routes. You should therefore never carry out the development and test tasks in the production system. To test and verify the developments, you should add a consolidation system to the system group. You’ll then have a three-system landscape, which is used by the majority of SAP ERP customers.

[»]  Landscapes with Multiple Production Systems

Some customers use several production systems, for example, to map regional structures with subsidiaries in various countries. However, in this section, we’ll focus on a three-system landscape with one production system.

When converting a single-system landscape, you must consider the entire system group. You’ll have to migrate every system in the system group to SAP S/4HANA to continue the necessary separation of tasks by individual systems in the system group in SAP S/4HANA.

We can’t provide general recommendations for migrating system groups because customer requirements differ considerably. Figure 10.4 therefore illustrates how to convert a system group in an abstract way.

First, you’ll convert the development and quality assurance (QA) systems to SAP S/4HANA. The SAP S/4HANA development system is usually a system copy of your existing development system in the SAP Business Suite landscape, converted to SAP S/4HANA.

During the development system conversion, you’ll adapt your business functionalities (for example, the credit management function if required) and custom developments as determined in the planning phase. These adaptations are recorded by transport requests and tested in the quality assurance system.

System Conversion in a Three-System Landscape

Figure 10.4    System Conversion in a Three-System Landscape

During the production system conversion, these transports are installed in the corresponding SUM phases to provide the necessary adaptations in the production system. You should carry out several test runs before you convert the production system so that you can test the entire procedure and specify measures to minimize production system downtime.

Figure 10.5 provides an overview of the various conversion runs for common system conversions:

  1. Initial test system conversion
    Usually, the first step of a system conversion project is to carry out tests in the sandbox system (for example, a copy of the PRD system). You’ll gain technical know-how about the conversion procedure in these tests, which you can use for subsequent conversions. End users can also make themselves familiar with SAP S/4HANA business functions in this system. In addition, you’ll analyze and test your custom developments based on the new software.
  2. Development system (DEV system) conversion
    In the SAP S/4HANA development system, you’ll adapt your custom developments to the SAP S/4HANA solution scope and data structures. You’ll also implement the mandatory adaptations in SAP S/4HANA if you have not already implemented them in the source system. To benefit most from the SAP S/4HANA conversion, you can implement further optional adaptations.
  3. Quality assurance system (QA system) conversion
    You’ll import adaptations from the DEV system (process adjustments and adaptations of the custom developments) and test the adapted business processes.
  4. Test run of the production system (PRD system) conversion
    You’ll test the production system conversion in the sandbox system under the same conditions that apply to your PRD system. In this context, you can prepare optimization measures for reducing downtime and can also develop and finalize the cut-over plan. You might have to repeat the tests several times.
  5. Production system conversion
    You’ll then convert the PRD system according to the specifications of your cut-over plan.
    Conversion Cycles in the System Group

    Figure 10.5    Conversion Cycles in the System Group

Before you convert the production system to SAP S/4HANA, you’ll have to keep the initial state of the SAP Business Suite system landscape, for example, to provide necessary corrections there. Consequently, you’ll maintain two development systems from the start of the SAP S/4HANA conversion project (development system conversion) up to the production system conversion. You can scale back the development system in the SAP Business Suite landscape when the production system conversion to SAP S/4HANA is complete. During this transition phase with two development systems, you’ll have to develop a strategy addressing how changes made in the SAP ERP system group during this time will affect SAP S/4HANA system group in the future.

Ultimately, the SAP S/4HANA system conversion does not pose new requirements to the software lifecycle management processes in a system group or to the definition of the transport routes between the systems.