If a company is considering migrating from an existing BW system to SAP BW/4HANA, its starting position is probably as follows: The majority of companies are currently running SAP BW 7.5, now that support for all BW releases older than SAP BW 7.5 has been discontinued. In addition, the company is faced with the task of discussing the future deployment type of the business intelligence landscape: Will the company stick with the on-premise approach with SAP BW/4HANA, or will it take the path toward the cloud?
In principle, both directions are conceivable: SAP has stated that both the on-premise option and the cloud variant will remain. So there are no plans to completely replace the existing on-premise systems with cloud solutions. What a company decides on also depends on strategic considerations. Depending on the decision, the on-premise variant leads to SAP BW/4HANA and SAP SQL Data Warehousing, while the cloud option focuses on SAP Data Warehouse Cloud. However, hybrid scenarios in which both approaches complement each other also have their justification. In this case, the company would sensibly extend its on-premise solutions with suitable cloud functionalities.
SAP itself apparently considers the hybrid approach, which involves the interaction of SAP BW/4HANA and SAP Data Warehouse Cloud, to be a sensible option. At the very least, the SAP BW/4HANA Service Pack 7 from December 2020 contains a number of adjustments that facilitate such interaction. This is where SAP BW/4HANA has its strengths to offer: Thanks to the openness of the system, data from almost any source can be connected. Data from the ERP system is extracted using ODP and processed in SAP BW/4HANA. Data from non-SAP systems is integrated via Smart Data Integration (SDI) with various adapters for the databases.
For companies using SAP BW 7.5, the early switch to SAP BW/4HANA is worthwhile for several reasons: SAP is implementing innovations exclusively in SAP BW/4HANA and no longer in earlier SAP BW versions. The interaction of SAP BW/4HANA and the latest ERP generation SAP S/4HANA simplifies numerous processes. In addition, the latest business warehouse generation from SAP offers a wide range of options for new types of modeling and objects as well as easier administration.
Accordingly, the question arises as to how best to make the switch. There are various ways to migrate to SAP BW/4HANA. Each company must decide for itself which is the right one against the background of its individual requirements.
Greenfield approach (new installation)
All reporting applications and objects are newly created based on SAP BW/4HANA. No data models are transferred from the previous BW system.
In-place conversion
The existing BW installation is migrated completely in the system and the system is then technically brought up to SAP BW/4HANA. Prerequisites are SAP BW 7.5 and a HANA database as well as the installation of the BW/4HANA Starter Add-on.
Remote conversion
First, the SAP BW/4HANA system is set up. In the second step, the data models to be converted from the legacy system to SAP BW/4HANA are selected.
Shell conversion
It is similar to remote conversion, but only the meta-objects are migrated, not data.
Landscape transformation (system consolidation)
Multiple BW systems are consolidated into one SAP BW/4HANA system. In practice, this is the rarest migration variant.
One of the crucial project phases for a successful migration to SAP BW/4HANA is the prepare phase, which prepares for the changeover. It gives companies the opportunity to find out many relevant details and analyze how the system will behave. Those who work conscientiously in the prepare phase save costs and prevent errors in the further course of the migration.
There are numerous steps that are required for the migration. With regard to the simplification items, it is necessary to check which BW objects can be migrated automatically to SAP BW/4HANA in the present modeling and which must be considered manually. From this analysis, the necessary work packages can be derived and the required effort can be realistically estimated. Working through the simplification items also offers the opportunity to clean up the system and delete objects that are no longer required.
Determining the migration method is also a fundamental part of the prepare phase. The choice of the appropriate method results from the analysis of the existing data models and the system conditions. It has proven helpful to use an evaluation matrix as a basis, which weights certain aspects relevant to the migration on the basis of points. A recommendation for a migration method can then be derived from the total number of points.
The tasks in the prepare phase also include checking the system requirements. The required activities include, for example, a sizing check, answering the question about the database platform and, if necessary, a release upgrade. With the SAP BW Checklist Tool for SAP HANA and the SAP Readiness Check for ODP, SAP provides helpful tools to get an overview of the system requirements.
Let’s assume a company has decided on remote conversion as a migration method based on the analyses in the prepare phase and the results of the evaluation matrix. In this case, there are now a number of work steps that we will highlight below.
First, the SAP BW/4HANA system must be installed. Likewise, the SAP Landscape Transformation Add-on (DMIS) must be installed on the sender and receiver systems. This tool takes care of the transfer from SAP BW to SAP BW/4HANA. The installation is carried out via Maintenance Planner and Software Provisioning Manager. Now the old SAP BW landscape and the new SAP BW/4HANA landscape exist in parallel.
The next step is to update the required SAP migration tools on the BW system using SAP Note 1909597 (SAP BW Migration Cockpit). It contains attachments with the current code. The manual update of the programs is performed using transaction SE38.
Now the authorizations have to be assigned. From experience, missing authorizations are the most frequent cause of problems during migration and lead to its termination. Successful migration requires various authorizations on the sender and receiver systems. For this purpose, roles with the required authorizations must be created. The corresponding SAP Note 2328530 contains an Excel file with all the necessary authorizations. It is imported into SAP BW as a role, and the authorization objects are defined in it. To import the many SAP notes, it is important to always use the latest service pack as the basis for the migration.
Now it’s time to run SAP Note Analyzer in the source, BW/4HANA and BW systems. Afterwards, the necessary SAP notes have to be implemented in the system.
To connect an SAP ERP system to SAP BW/4HANA, the ODP source system must be created. This completes the prerequisites for the migration.
Now the actual migration begins. The sixth step involves setting up an RFC connection between the SAP BW and SAP BW/4HANA systems and creating the transport rail between the two systems. It should be noted that RFC users require special authorization.
This is about defining the scopes and setting up a sensible sequence for the migration. Central data flows and applications should be migrated first.
The final section involves preparing the BW applications. Some BW applications cannot be migrated automatically with the transfer tool. The modeling must be adapted to conform to BW/4HANA, and new modeling may also be required.
With the right preparation and the earliest possible elimination of possible errors in the prepare phase, the subsequent migration to SAP BW/4HANA is no longer a problem. In fact, many difficulties during the migration can be traced back to the fact that work was not done properly in the prepare phase. The prepare phase provides a good overview of the work packages, prepares the system for migration, provides a risk assessment of the methods, offers the possibility of a realistic effort estimate and analyzes the simplification items. The biggest benefits resulting from a carefully managed prepare phase are lower costs and a faster and smoother migration to SAP BW/4HANA.