Preparing for the conversion to SAP HANA

Excerpt from SAP BW/4HANA and BW on HANA by Klaus-Peter Sauer and Frank Riesner.

Before you make the decision to use SAP HANA as the database for your Business Warehouse — or at the latest when you actually make the decision — you should address topics such as the sizing, migration, housekeeping, and data center operation of SAP HANA as the database for your BW system.

Ideally, you will have discussed these topics before making the decision for SAP HANA. The sizing, for example, is a decisive factor not only for the size and number of servers required — depending on the licensing model, the size of the database may also influence the license costs. Regardless of the licensing model, you should establish housekeeping (see Section 2.3) as a permanent process in the company. This will allow you to keep system tables lean.

2.1 Sizing
In recent years, we have been involved in the sizing of many BW on HANA systems. By far the most common case is the migration of an existing BW system to SAP HANA, referred to as the brownfield approach. The greenfield approach, in which a new BW is considered only on an SAP HANA system is less frequent. The transfer of a non-SAP data warehouse (DWH) to a BW system is rare, and we therefore address this approach only very briefly.

It is important to make sure that you size the database server for SAP HANA correctly because many mistakes can be made at this point. To help you avoid this, Marc Bernard, Product Manager SAP EDW, has written a very good blog detailing the most common errors made when sizing a BW on HANA system.

Blog: How NOT to size an SAP BW system for SAP HANA
https://blogs.sap.com/2013/08/28/how-not-to-size-a-sapnetweaver-bw-system-for-sap-hana/

2.1.1 Sizing when migrating an existing BW system
When migrating existing BW systems to SAP HANA, we strongly recommend that you use the ABAP sizing report for the database sizing. This report guarantees more accurate results and it is independent of the database compression. It can also incorporate the concept of non-active data, extended tables (for details on both topics, see Section 4.1), as
well as future growth. SAP Note 2296290 and the attachments to that note describe in great detail how to run the report and what the functions of the individual parameters are.

The sizing report is called /SDF/HANA_BW_SIZING and is delivered from Service plug-in ST-PI 2008_1_7xx SP8 or ST-PI 740 SP01. The minimum prerequisite for the report is NetWeaver BW 7.0 SP1. For BW 3.5 systems, there is a separate report (SAP Note 2021372). You can use different parameters for the report, which means that you have good control over the required resources and thus the load on the system. The report also saves you a lot of work by, for example, considering influences such as the conversion to unicode and any potential compression of the source database automatically. You can also run the report just for certain subareas of the system if you are planning to migrate only part of your system.

We recommend that you run the report and specify growth values based on your experience from previous years. This will give you a better overview of the hardware requirement for the coming years. Experience shows that the usual values for annual organic growth are between 10% and 30%. We also recommend that you activate consideration of nonactive data.
With regard to the precision level, Low is sufficient to give meaningful results. It is only for small systems with databases of less than 500 GB that we recommend you set this level to High.

As already mentioned, SAP Note 2296290 contains very good documentation with an example. It gives a detailed description of all input parameters, how the tool works, and the results. Therefore, we will not provide any further explanations or an example at this point. We will restrict ourselves to typical questions or important information that we often receive despite using the detailed sizing report.

Up-to-date database statistics
We strongly recommend that you run the sizing report only with up-to-date database statistics because otherwise the results will be incorrect.

With regard to sizing, one aspect that is often forgotten is that every server has an operating system with a certain main memory requirement. 10% of the first 64 GB and 3% of the remaining main memory is reserved for the operating system. Furthermore, 50 GB must be reserved for services and caches for each server node. This results in the values shown in Table 2.1 for the different server sizes currently available. The sizing report takes these values into account fully automatically.

Table 2.1: Available main memory for different server sizes

Scale-out configurations for BW systems have at least three computer nodes. As a minimum, we strongly recommend two worker nodes for one master node. For more information about scale-out, see Section 2.4.2 on Scalability. Additional details about the sizing of the master node and the optimum number of scale-out nodes can be found in SAP Notes 1855041 and 1702409.

The sizing of the application server
With regard to the sizing of the application server, initially there is no change compared to a BW system with a different database. This applies to both ABAP application servers and JAVA application servers. You can use the Quick Sizer (see the next section) to work out the size for these servers.

Sizing additional applications and projects
If you want to operate further applications in BW (e.g., BPC) or on the same SAP HANA database (MCOD, see Section 2.4.3) in the future, you have to consider the main memory requirement for these applications in addition to the sizing of the BW system.

This also applies for new projects: in this situation, further data enters the system and you should include this in your considerations additively. If you are intending to consolidate multiple BW systems, you should also consider this additively. A useful side effect of the sizing report is that it provides information about the volume of data in certain objects. In the case of very large row stores, change logs, or PSA tables, you can quickly see whether a system is well-maintained. For more on the topic of housekeeping, see Section 2.2.7.

Sizing reports for BW on HANA
Always use the latest version of the sizing report. The report is constantly being improved and only the most up-to-date version will guarantee the highest possible accuracy.

New sizing report for BW/4HANA

https://launchpad.support.sap.com/#/notes/2296290
Sizing Report for BW on HANA (for BW 3.5 Systems): http://service.sap.com/sap/support/notes/2021372

SAP HANA Academy: “BW on HANA” sizing video
This video provides a step-by-step procedure for using the sizing report: https://youtu.be/-qq6d92YJek

Keep reading in SAP BW/4HANA and BW on HANA.

SAP BW/4HANA has introduced a new era in data warehousing at SAP. Further steps towards simplification, flexibility, and performance are now possible with SAP HANA as the proven technological basis. SAP BW/4HANA offers modern concepts for data management, operation, and modeling and thus opens the door for fully innovative application scenarios.

This book will show you how the SAP HANA database influences the Business Warehouse and how you can optimize your system. As a practical guide, the book is aimed at experienced SAP BW experts as well as decision makers who need a well-grounded overview. The authors address the versions SAP BW/4HANA 1.0 and SAP BW 7.5 in equal measure, highlighting new functions and differences. The book also focuses on the migration options and conversion tools for moving to SAP BW/4HANA.
Use this reference book to enter the world of SAP BW with SAP HANA as the database platform!

– Migration, sizing, operation, data management with SAP BW/4HANA and SAP BW 7.5 on HANA
– The new central source Systems SAP HANA and ODP
– New modeling options, mixed scenarios, LSA++, and differences compared to SAP BW 7.5
– The role of BW in operational SAP reporting

Start reading now!

Author Klaus-Peter Sauer works as a Director in the global SAP HANA Center of Excellence (COE) at SAP, focusing on the topics of data warehousing, SAP BW, and big data in connection with the SAP HANA platform. He started his career in 2000 as an SAP BW consultant, whereby over the course of time, he has taken up various key positions, both in Consulting and in pre-sales. As the technical lead of the SAP COE in EMEA at Teradata, Klaus-Peter supported leading companies in all industries in implementing future-proof and cross-platform data warehousing architectures. Since 2012, he has been part of a global expert team for the SAP HANA platform, data warehousing, and big data at SAP.  Klaus-Peter has a Master’s degree in Business Administration from the Canterbury Business School in Great Britain. He studied Economics and Business Informatics at Philipps-Universität in Marburg, Germany and the University of Kent at Canterbury, Great Britain.

Author Frank Riesner has been engaged in the area of SAP Business Intelligence, focusing on SAP Business Warehouse, since 2002. As a Senior Architect and Trainer at SAP (Switzerland) AG, his tasks involve SAP HANA in the context of enterprise data warehousing and business analytics. His role includes accompanying customer projects, supporting sales activities, and appearing at events as a speaker. Frank is also regularly engaged by SAP Education to hold courses in Switzerland and abroad, with responsibility for the curriculum of SAP BW/4HANA, including conceptual responsibility. Frank studied Business Informatics at the University of Bamberg, Germany, and after completing his degree in 2002, was employed for a few years as a Senior Consultant for SAP BW at Inforte GmbH and at Steria Mummert Consulting AG in Germany. Frank then worked freelance in the same role for five years in Budapest, Hungary, before taking up his current role at SAP (Switzerland) AG as Delivery Manager for an Outsourcing service provider in Switzerland. He currently lives in Basel and is married with two children.