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Client/Server Principles

In SAP terminology, a service means a service provided by a software component (software-oriented view). This component can consist of a process (compare work process) or a group of processes (compare application server) and is then called a server for that service. Software components that use this service are called clients. At the same time, clients can also be servers for specific services. A server often also means a computer (host) on which software components that provide specific services are running (hardware-oriented view).
Client Server Principles

SAP System Client/Server Configurations

The fundamental services in a business application system are presentation services, application services, and database services. In a one-tier SAP configuration, all processing tasks are performed on one server, as in classic mainframe processing. Two-tier SAP System configurations are usually implemented using special presentation servers that are responsible solely for formatting the graphical user interface. Many SAP System users use Windows PCs for example as presentation servers. An alternative two-tier configuration (not shown) is to install powerful desktop systems and to use these for presentation and applications also (two-tier client/server). This type of configuration is particularly useful for processing-intensive applications (such as simulations) or for software developers, but due to the additional administration requirements is usually used for test purposes only.

In a three-tier configuration, separate servers are used for each tier. Using data from the database server, several different application servers can operate at the same time. To ensure that the load on individual servers is as even as possible and to achieve optimal performance, you can use special application servers for individual application areas such as distribution or financial accounting (logon and load balancing).
Client Server Configuration

SAP Database Interface

Today, large amounts of data are usually administered using relational database management systems (RDBMS). These systems store the data and the relationships between the data in two-dimensional tables, which are known for their logical simplicity. The definitions of the data, tables, and table relationships are stored in the data dictionary of the RDBMS.
Within ABAP, SAP OPEN SQL is used to access application data in the database, independent of the corresponding RDBMS. The SAP database interface converts the open SQL statements from the ABAP statements into the corresponding database statements. This means that application programs written in ABAP are database-independent. Native SQL commands can be used in ABAP.
When interpreting open SQL statements, the SAP database interface checks the syntax of these statements and automatically ensures the local SAP buffers in the shared memory of the application server are utilized optimally. Data frequently required by the applications is stored in these buffers so that the system does not have to access the database server to read this data. In particular, all technical data such as ABAP programs, screens, and ABAP Dictionary information, as well as some business process parameters usually remain unchanged in a running system, making them ideal buffering candidates. The same applies to certain business application data, which is accessed as read-only
SAP Databae Interfaces

SAP Application Services

The operating system views the SAP runtime system as a group of parallel, cooperating processes. On each application server these processes include the dispatcher as well as work processes; the number of work processes depends on the available resources. Work processes may be installed for dialog processing, update, dialog free background processing and spooling.
In addition to these work process types (dialog processing (D), update (V: for the German “Verbuchung”), lock management (E), background processing (B), spool (S), the SAP runtime system provides two additional services for internal and external communication (below are the restrictions on the number of work processes):
The message server (MS or M) communicates between the distributed dispatchers within the SAP System and is therefore the prerequisite for scalability using several parallel-processing application servers.
The gateway server (GW or G) allows communication between SAP, R/2 and external application systems.

  • Dialog: Every dispatcher requires at least two dialog work processes
  • Spool: At least one for each SAP System (more than one allowed for each dispatcher)
  • Update: At least one for each SAP System (more than one allowed for each dispatcher)
  • Background processing: At least two for each SAP System (more than one allowed for each dispatcher)
  • Enqueue: Only one enqueue work process is needed for each system

SAP Application Hierarchy

You can view the Repository structure in the application hierarchy. You can navigate to the application hierarchy from the initial screen using Tools -> ABAP Workbench -> Overview -> Application Hierarchy. (Transaction SE81).
The application components are displayed in a tree structure in the application hierarchy. Expanding a component displays all the development classes that are assigned to that component.
You can select a sub-tree and navigate from the application hierarchy to the Repository Information System. The system then collects all development classes for the sub-tree selected and passes them to the Information System.

Logging on to the SAP system

SAP LogonThe SAP System is a client system. The client concept enables the joint operation, in one system, of several enterprises that are independent of each other in business terms. During each user session you can only access the data of the client selected during the logon.
A client is, in organizational terms, an independent unit in the SAP System. Each client has its own data environment and therefore its own master data and transaction data, assigned user master records and charts of accounts, and specific customizing parameters. A user master record linked to the relevant client must be created for users to be able to log on to the system. To protect access, a password is required for logon. The password is hidden as you type (you only see asterisks).

SAP systems are available in several languages. Use the Language input field to select the logon language for each session. Multiple logons are always logged in the system beginning with Release 4.6. This is for security as well as licensing reasons. A warning message appears if the same user attempts to log on twice or more. This message offers three options:

  • Continue with current logon and end any other logons in the system
  • Continue with current logon without ending any other logons in the system (logged in system)
  • Terminate current logon

SAP Screen Elements

SAP Screen Elements

Command field: You can use the command field to go to applications directly by entering the transaction code. You can find the transaction code either in the SAP Easy Access menu tree (see next slide) or in the relevant application under System® Status.
Menu bar: The menus shown here depend on which application you are working in. These menus contain cascading menu options.
Standard toolbar: The icons in the system function bar are available on all SAP screens. Any icons that you cannot use on a particular screen are dimmed. If you leave the cursor on an icon for a moment, a small flag will appear with the name (or function) of that icon. You will also see the corresponding function key. The application toolbar shows you which functions are available in the current application.
Title bar: The title bar displays your current position and activity in the system.
Check boxes: Checkboxes allow you to select several options simultaneously within a group.
Radio buttons: Radio buttons allow you to select one option only.
Status bar: The status bar displays information on the current system status, for example, warning and error messages.
A tab provides a clearer overview of several information screens.
Options: You can set your font size, list colors, and so on here.

SAP Easy Access Standard

SAP Easy Access
SAP Easy Access is the standard entry screen displayed after logon. Using the menu path Extras® Set start transaction you can select a transaction of your choice to be the default entry screen after logon.
You navigate through the system using a compact tree structure that you can adapt to your own specific requirements. Use the menu path Extras® Settings to change your view of the tree structure. You can use this to display technical names (transaction codes).

You can also create a Favorites list of the transactions, reports, files and Web sites you use most.
You can add items to your favorites list using the Favorites menu option or by simply dragging & dropping them with the mouse.

SAP Transactions

  • Transactions form the basis of SAP program processing.
  • A transaction is the smallest step that can be executed by the user.
  • 4 – 20 character transaction codes are commonly used to quickly access specific screens in SAP.
  • Transaction codes are entered in the OK (Command) field in the SAP System.
  • A number of commands are provided to facilitate SAP session management and transaction processing
  • Transaction codes are stored in table TSTC.
  • The transaction code of a particular screen can be easily identified by accessing the System menu and choosing the “Status” option. The transaction code will be displayed in the”Sap Data/Repository Data/Transaction” field.

Example Transaction Codes:
SE80 – Repository Browser
SE38 – ABAP Editor
SE11 – ABAP Dictionary
SM04 – Overview of Users

OK Field Commands:
/o – Lists user’s sessions
/oxxxx – Creates a new session and starts transaction xxxx
/n – Cancels current transaction
/nxxxx – Cancels current transaction and starts transaction xxxx
/h – Turns on Debugger mode
/nend – Logs off
/i – Deletes current session

SAP Sessions

A “session” is an independent window to work in. Multiple sessions allow several tasks to be worked on at once. To open a new session, select “Create session” from the System menu or use transaction “/oxxxx”. Each user can have up to six parallel sessions open.
When logging on to a system with more than one user ID, or onto multiple clients on the same system (for example, some servers have one client for coding and another client for testing) be sure not to confuse the different sessions!

SAP General System Functions

SAP General System Functions

  • Create session – starts a parallel session
  • End session – terminates the current session
  • User profile – provides user info (defaults, address, parameters)
  • Services – start reports, display and maintain tables
  • Utilities – access to debugger, SQL trace, resource usage
  • List – find character string, download code, print, save to reporting tree
  • Workflow – Access SAP Workflow
  • Own spool requests – shows spool request for specified selection
  • Own job – displays status of the SAP user’s background jobs
  • Short message – allows the user to send a message to another SAP user
  • Status – displays user & system data (eg., current screen/transaction code etc.)
  • Log off – closes all parallel sessions for current logon ID

The system menu can be accessed from all SAP transactions. The System Services menu contains, among others, the following options:

  • Reporting: Starts reports (ABAP programs).
  • Output controller: This is where you manage user-specific print requests.
  • Table maintenance: This is where you process tables and views.
  • Batch input: Administers batch input sessions and data transfer.
  • Jobs: This is where you can administer jobs that are processed in the background.
  • SAP Service: Enables you to log on to SAP’s SAPNet SAP Frontend

SAP Help on Screen Fields

SAP Help
Users can get help on fields by pressing “F1” or clicking the help button on the toolbar when the cursor is positioned in the field in question. A list of possible entries for a field can be obtained by pressing “F4” or clicking the arrow to the right of the field (see diagram, left). To select a value from the possible entry list, double click the entry or position the cursor on the value and press “F2”.

Users can get object-specific information (for example, about fields, new options, messages, etc.) anywhere in the system by positioning the cursor on the relevant object and pressing F1. Search helps are ABAP dictionary objects designed to provide the users with a mechanism to search for and then select the appropriate field values. Search helps are used to define input help (F4 help) for screen fields. Search fields are fields whose possible input values are sought in the possible entries (F4 help) process.

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