Describing the Architecture of SAP Systems

It is possible for the same SAP systems to be integrated in different applications. An application is therefore a type of logical container around a set of SAP systems.

The old, existing SAP world is the SAP Business Suite, consisting of the applications SAP ERP, SAP CRM, SAP SRM, SAP SCM, and SAP PLM.

Successor of SAP Business Suite are (among others) SAP S/4HANA and SAP BW/4HANA.

Most traditional enterprise relational database tables are based on row storage, as this is regarded as the optimal storage design for an online transactional processing (OLTP) application. An OLTP application requires fast, record-level updates where all columns in the record are usually needed for processing.

SAP HANA fully supports OLTP applications using row storage but also supports columns based storage which is the optimal storage design for online analytical processing (OLAP) applications. OLAP applications typically work with high-volume tables that need to be quickly aggregated by ad-hoc queries.

The database of SAP HANA supports both row tables and column tables in the same database. Modern applications, such as SAP S/4HANA, combine transactions and analytics so SAP HANA, with its row and columns storage, is the ideal database on which to build such applications.

Column tables are efficient for analytical applications where requests for selections of data are not predictable. Queries from analytical applications that are sent to the database often require only a subset of the overall data in the table. Usually only a few columns are required from the table and also only a limited number of entries from the columns are needed. With column tables, only the required columns are loaded to memory, so you avoid filling up memory with columns that will never be used. Also, the data is arranged efficiently with all values of a column appearing one after another. This continuous sequencing of the column values is preferred by the CPU, which is able to scan the values efficiently without having to skip over unwanted values.

With column store, SAP HANA scans columns of data so quickly that additional indexes, although supported, are usually not required. This helps to reduce the complexity by avoiding the need to constantly create, drop and rebuilding separate indexes.

It is easy to alter column tables, for example, by adding extra column or removing columns, without dropping and reloading data.

Column tables are optimized for parallel processing, as each CPU core is able to work on a separate column.

The downside to column tables is the cost of reconstructing complete records from the separately stored columns. Reconstruction typically occurs in transactional applications that requires the complete record for updating, copying, or deletion. Although it is possible to build transactional applications on column tables, you might see better performance if you were to use row-based tables where all the columns in a record are always held together and can be read in one step.

But more often these days, applications combine transactional and analytical elements. In this case, you must decide which is the best storage method to use. You cannot have a table that is both row-based and column-based.

Most SAP systems are based on the Application Server ABAP or Application Server Java and use it as the runtime environment.

SAP systems are used for mapping business processes or business applications. Implement these applications independently of the hardware environment used (operating system, database) to the greatest extent possible. SAP provides two different runtime environments for this, an ABAP runtime environment (usage type AS ABAP), and a Java runtime environment (usage type AS Java).

Before we discuss various client/server configurations in the context of SAP systems, we first need to define the concepts client and server. There are two ways of doing this.

• In the hardware-oriented view, the term server means the central server in a network that provides data, memory, and resources for the workstations (clients).

• In the software-oriented view, client and server are both defined at the process level (service). A service in this context is a service provided by a software component. This software component can consist of a process or a group of processes (such as an Application Server ABAP) and is then called a server for that service. Software components that use a service are called clients. At the same time, clients can also be servers for other specific services.

The following figure clarifies the two approaches to the definitions.

In the context of SAP systems, the terms client and server are generally used as defined in the software-oriented view.

The following processes are often used for operating business application software:

• Presentation processes (for example, for displaying screens)

• Application processes (for example, for executing application programs)

• Database processes (for example, for managing and organizing database data)

When you are installing and configuring an SAP system, decide how you are going to distribute the required processes among the available hardware. Configurations are either single-tier or multi-tier, depending on the number of hardware layers used. The SAP ECC system is an example of business application software.

Single-tier configurations are generally used for tests and demonstrations (for example, an SAP system on a laptop). If many users want to work on a system configured in this way, then the extra hardware costs for each additional user become greater than the costs associated with implementing additional hardware levels (for example, moving the presentation processes to other hosts).

The two-tier configuration with distributed presentation processes can maintain good performance for a significantly higher number of users, without substantially increasing the hardware costs. The load resulting from the presentation processes is distributed to the various front-end computers and so does not influence the performance of the database host.

However, if the number of users exceeds a certain upper limit, the central host, on which both application and database processes run, risks becoming a bottleneck. To prevent this, you can improve the performance of the SAP system by distributing the application-layer processes to several hosts. Another advantage of adding a hardware layer specifically for application processes is that it facilitates scalability. If the number of SAP users in an SAP system increases over time, negatively affecting SAP system performance, then this problem can, in most cases, be solved simply by adding another host for application processes.

An alternative two-tier configuration is to install powerful desktop systems and to use these for presentation and applications (two-tier client/server). These configurations are especially suited to applications with high processor demands (for example, simulations or for software developers), but are not implemented in the SAP environment, other than for test purposes, due to the additional administration required.

In the SAP S/4HANA and SAP Business Suite environment, more complex client/server configurations consisting of more than three tiers are both theoretically possible and used in practice. An additional level could be a Web server, for example.