SAP BW – A Relict of the Past?
The Business Suite successor S/4HANA has fundamentally changed the purpose of SAP BW as a data warehouse. What are the integration scenarios between BW and S/4? Are Hana-based SAP applications already delivering on the promise of unifying OLAP and OLTP?
As early as 2009, a full year before the first Hana release, SAP co-founder Hasso Plattner published the groundbreaking white paper “A Common Database Approach for OLTP and OLAP Using an In-Memory Column Database”. In it, he questioned the long-standing practice of separating OLTP and OLAP applications. According to his theory, a column-based in-memory database could be used by both transactional and analytical applications. When SAP Hana was announced in 2010, unifying the two was the stated goal on every SAP Hana roadmap. At the same time, SAP is working to advance data analytics on transactional systems (known as operational reporting). With operational reporting, SAP has created a means to analyze data without having to transfer it to a BW system first. This reduces the workload on the BW system and makes real-time analytics a reality. Every Business Suite on Hana customer gets free access to Hana Live content to allow Hana-optimized operational reporting from within the Business Suite. Hana Live is a combination of a virtual data model based on SAP’s standard tables and a user interface to put it to use.
S/4HANA also includes a very similar solution, but with a different technological foundation. Other than Hana Live, the virtual data model behind “Embedded Analytics” is not defined at the database level, but rather on the application server. This eliminates the time-consuming burden of having to maintain authorizations in both the database and the application server. But even as S/4HANA systems continue to bring together an ever-larger number of features previously provided by separate modules, Embedded Analytics alone will not be able to meet a company’s demanding reporting requirements for the foreseeable future. It lacks a data warehouse to incorporate and harmonize data from other systems. There is still no way around a BW.
BW and S/4
There are different ways to set up a system landscape with S/4HANA and SAP BW. The different approaches differ mainly in terms of data extraction into the BW system and administrative hassles. The following three scenarios are feasible:
The traditional approach: BW and S/4
It is still possible to run a completely separate BW system in an S/4 landscape. The introduction of an S/4HANA system, however, necessitates extensive modelling changes: Currently, S/4HANA does not provide the BW extractors that are included in the Business Suite (as of S/4HANA 1511). Instead, this requires direct access to the database-level tables. This can be achieved by regularly synchronizing the data between S/4HANA and the BW database. One needs to keep in mind though that this is a very time-consuming process that often results in obsolete data in the BW system. In the case of an BW on Hana system, however, it is possible to use the Smart Data Access (SDA) functionality in Hana instead. SDA allows users to access different databases and other Hana instances alike. For this purpose, a virtual table is created to point non-persistent, read-only access and write access to the target database. In the BW system, virtual tables can, for example, by re-used by Open ODS views.
The shared databased approach: MDC
Another possibility is to use separate application servers, leveraging the same database in a multi-tenant database container (MDC) scenario. Ever since the release of service pack stack 09, Hana is capable of running multiple client databases (tenants). Today, running multiple SAP applications in parallel on the same database instance is officially supported. Detailed information on this scenario can be found in SAP note 2096000. A white list of other applications that can be combined based on MDC is available in SAP note 1661202.
The MDC concept also requires the transfer of data from S/4HANA and BW at the database level. For this purpose, SAP recommends using the Hana SDA (Smart Data Access) approach described above. The transfer of the data, however, unnecessarily ties up valuable resources as SDA is designed to communicate with different databases on other servers. So instead of reading the data of the other tenant within the Hana instance, SDA creates a new database connection and transfers the data through the network stack of the operating system. But given the fact that a multi-tenant Hana database is indeed capable of directly transferring data between the different tenants, it is likely that SAP will add native functionality for the integration of data from other Hana tenants in BW with future releases. In both cases, data extraction from S/4HANA is faster than it is in traditional system environments, as they eliminate network communication between multiple servers.
Shared operation: Embedded BW
Like the Business Suite starting from NetWeaver version 7, S/4HANA also contains an “embedded BW”. It includes the same transactions and features of a standalone BW, but runs on the same application server. It is commonly used on a separate client. SAP, however, currently recommends that embedded BW be used exclusively for operational reporting purposes, even though it does allow for the integration and processing of data from third-party systems just like any traditional BW system does. The use of embedded BW systems for enterprise-wide reporting has so far been a rather unusual scenario because it presents new challenges in terms of administration and system utilization. While the introduction of the MDC concept has finally opened up the possibility of explicitly using Hana to run multiple applications in parallel, there is still little hands-on experience on how to size application servers that host both analytical and transactional processes. It is also important to note that the maximum size of S/4HANA systems is limited because scale-out scenarios, that is, adding additional servers to increase database size, have not yet been approved for S/4HANA. What’s more, NetWeaver and database updates will always impact both components. This translates into longer downtime and increases the burden of preparatory and follow-up work. Embedded BW is already used in the S/4HANA standard. One of its use cases is to allow reporting based on Hana Views that are predominantly used in the Finance component of S/4HANA.
S/4HANA has not eliminated the need for a BW system to allow for enterprise-wide reporting across multiple systems. Companies migrating from an existing SAP Business Suite installation need to completely overhaul the way they extract data into the BW system. Since at this point S/4HANA does not make available any extractors for SAP BW, the data has to be transferred at the database level. Consequently, embedded BW appears to be an interesting solution for S/4HANA customers. What this scenario also does, however, is add to the administrative burden associated with the shared application server. Also, as of now, the maximum size of an S/4HANA installation is still limited. And even though implementing an MDC scenario means increasing the speed of extraction into the BW system by eliminating associated network data traffic, there is still no native functionality to transfer data between the Hana tenants in the BW system. Other than with the application itself, administration tasks always affect both database instances, making this approach much more complicated. It does, however, still present a reasonable compromise between the other two solutions. It remains to be seen how SAP will continue to develop these scenarios in the years to come and whether customers will embrace operational reporting and with it embedded BW for their enterprise-wide reporting.
By Steve Blum, Consultant at Camelot ITLab
The original article was published in E-3 OKTOBER 2016.