21. Response Time

Response Time

The time it takes to get from step 1 (user request) to step 7 is known as response time. The response time is one of the main indicators of how healthy (well−tuned) the system is.

A SAP instance profile parameter controls the maximum allowed time for interactive execution of a dialog step: rdisp/max_wprun_time.

The default value for this parameter is 300, When this value is reached, the dispatcher stops the work process and the user gets a TIME_OUT error.

20. SAP Instance

SAP Instance

An instance is an administrative entity that groups together R/3 components which offer one or several services. These offered services are started or stopped together. All instance components are configured using a common instance profile.

In sap there are two types of instance central instances and dialog instances SAP distinguishes between central instances and dialog instances. Every SAP system has just one central instance, which contains all basic services such as the message server, gateway, update, enqueue, dialog, spool, and background right from installation. Dialog instances, as defined, only contain a set of basic services such as dialog and background work processes from the time of installation.

19. Memory Area

Memory Area

SAP use following type of memory

01. Physical :- (RAM) OS, WP, Listener. 
02. Extended: - (Hard disk) Database. 
03. Virtual: - (Page file) CI.

18. DIAG PROTOCOL

DIAG PROTOCOL

The connection between the SAPGUIs and the SAP dispatcher is made with an optimized protocol, known as DIAG, in which small data packages are sent through the network.

17. Gateway Server

Gateway Server

The gateway service allows the communication between R/3, R/2, and external applications. This service is a CPIC handler which implements the CPIC protocol for communication.

16. Message Server

Message Server

The message server is a service used by the different application servers to exchange data and internal messages.

Every application server has a unique name for the message server.

The location of the host running the message server is configured in the DEFAULT.PFL common profile. The parameter is rdisp/mshost = <hostname>.

15. Update Work Process

Update Work Process

The update work process is in charge of executing database changes when requested by the dialog or background work processes.

An update request can contain a primary update component (V1) and several secondary ones (V2). The time critical processes are held inside the V1, the less critical within the V2. In order to be able to initiate the V2 components of the log record, the V1 component must have finished.

The other parameters, rdisp/wp_no_vb and rdisp/wp_no_vb2

14. Enqueue Work Process

Enqueue Work Process

Commonly there is only one enqueue work process for a single SAP system; however there are circumstances where, for performance reasons, it might be useful to configure up to four enqueue work processes. R/3 note 127773 contains more details about this.

The profile parameter that controls the number of enqueue work processes is: rdisp/wp_no_enq

The locks (enqueues) are managed by the enqueue work process using a lock table which resides in the main memory. When the processes receive a locking request, the enqueue work process verifies whether the requested lock object interferes with other existing entries in the lock table.

The lock objects are special types of objects defined in the ABAP dictionary.

 Type of Lock

	Lock mode	Description
Shared lock	S (Shared)	Several users (transactions) can access locked data at the same time in display mode. A request for another shared lock is accepted, even if it comes from another user. An exclusive lock set on an object that already has a shared lock will be rejected.
Exclusive lock	E (Exclusive)	An exclusive lock protects the locked object against all types of locks from other transactions. Only the same lock owner can reset the lock (accumulate).
Exclusive but not cumulative lock	X (eXclusive non-cumulative)	Exclusive locks can be requested several times from the same transaction and are processed successively. In contrast, exclusive but not cumulative locks can be called only once from the same transaction. Each further lock request will be rejected.
Optimistic lock	O (Optimistic)	Optimistic locks initially behave like shared locks and can be converted into exclusive locks

When the lock objects are defined in the dictionary, there are two ABAP function modules automatically generated for them: one to lock the object (enqueue) and another function to unlock it (dequeue). These functions are called at the beginning and at the end of a transaction respectively.

If for some reason there are problems between the locking and unlocking of an object, it remains locked until the administrator manually deletes the lock by using tcode SM12.

13. Spool Work Process

Spool Work Process

The spool work process is in charge of formatting the data for printing and passing it to the host spool system.

The spool requests, indicating the printer and the printing format of the spool request, are generated during dialog or background processing and are held on the spool database. The data itself is kept in a special area, known as TemSe (temporal sequential objects).

The SAP profile parameter that controls the number of spool work processes per instance is rdisp/wp_no_spo

12. Background Work Processes

Background Work Processes

The background work processes are in charge of executing ABAP programs submitted for background execution.

The SAP profile parameter that controls the number of background work processes per instance is rdisp/wp_no_btc.

RDDIMPDP is a program which checks scheduled background jobs it run every 60 second. Profile parameter for this is btctime.

11. Dialog Work Processes

Dialog Work Processes

A dialog work process performs the dialog steps corresponding to the interactive user sessions.

The SAP profile parameter that controls the number of interactive dialog work processes per instance is rdisp/wp_no_dia. Minimum two dialog work required per dispatcher.

A dialog work process can support from 5 to more than 10 simultaneous users each.

Data flow in dialog steps.

10. Work Process and its type

01. Work Process

The work processes are special programs in charge of some specific tasks. Using client/server terminology, a work process is a service offered by a server and requested by a client.

Work processes make use of two special areas: paging and roll. The paging area holds application program data such as internal tables or report listings. The roll area holds the user context data entered in previous dialog steps and other control and user information such as authorizations. Where there is main memory available, these areas are held in the main memory of application servers; otherwise they are paged out or rolled out to physical disk files.

02. Work Processes Types

There are several types of work processes: dialog, background, update, enqueue, and spool. Additionally, the R/3 runtime system includes three other special types of services: message service, gateway, and the system log collector.

A group made of a dispatcher and a set of work processes is known as the application server.

Tcode to monitor work process is SM50

09. The Dispatcher

The Dispatcher

The SAP dispatcher is the control program which manages the resources of the R/3 applications. It works like a typical transaction monitor which receives screens and data from the presentation services and passes them to the corresponding work processes.

The main tasks of the dispatcher are as follows:

• Balanced assignment of the transaction load to the work processes
• Buffer management in main memory
• Connection with the presentation level
• Organization of the communication processes

The logical flow of execution of a user request follows:

1. Users enter data in their presentation server; the data is received by the SAPGUI, converted to a SAP format, and sent to the dispatcher using an special optimized protocol called DIAG.

2. Initially, the dispatcher keeps the requests in queues, where the dispatcher later processes them one by one.

3. The dispatcher allocates the user requests using the free work processes. The real execution takes place inside the work processes themselves.

4. At the end of execution, the result of the work process task goes back to the SAPGUI through the dispatcher. SAPGUI interprets the received data and fills up the user screen.

SAP has optimized the data flow between the presentation and the application servers. Typically the quantity of data that goes in the network from the dispatcher to the SAPGUI does not exceed 2K (for dialog processes). This network traffic does not include the print requests that are managed by spool or print managers on users' PCs or workstations.

08. SAP Kernel

SAP Kernel

The kernel is a computer program that constitutes the central core of a computer's operating system. It has complete control over everything that occurs in the system. As such, it is the first program loaded on startup, and then manages the remainder of the startup, as well as input/output requests from software, translating them into data processing instructions for the central processing unit.

It is also responsible for managing memory, and for managing and communicating with computing peripherals, like printers, speakers, etc. The kernel is a fundamental part of a modern computer's operating system.

In the SAP system kernel are a group of software programs running as daemon processes in the UNIX operating system or as services on Windows NT.

07. SAP System Client

SAP System Client

A client is an area containing independent application data within as SAP system. This is defined as a legally and organizationally independent unit within the R/3 system, for example, a company group, a business unit, or a corporation.

SAP comes with three standard clients: 000, 001, and 066.

000 is a special client for the R/3 system since it contains the client independent settings.

001 is a copy of the 000 client

066 is reserved for SAP access to its customers' systems . After ECC6 client 066 removed.

06. Logical Units of Work (LUWs)

Logical Units of Work (LUWs)

Conceptually, a logical unit of work (LUW) is defined as an elementary processing step which works as a locking mechanism to protect the transaction's integrity. A LUW is a set of steps within a transaction, and all of those steps must be correctly completed to go ahead with the transaction logic. If there are errors before the end of the transactions, the current LUW is canceled, but not the previous ones.

05. Dialog Step

Dialog Step

A dialog step is a SAP R/3 screen, which is represented by a dynpro. A dynpro, or dynamic program, consists of a screen and all the associated processing logic. It contains field definitions, screen layout, validation and processing logic, and so forth. A dialog step is controlled exactly by a dynpro.

The processing logic means that the dynpro controls what has to be done before the screen is displayed (process before output or PBO) and what has to be done after the user finishes entering information (process after input or PAI).

When users are navigating in the SAP R/3 system from screen to screen, they are actually making dialog steps. A set of dialog steps makes up a transaction.

04. Transaction Code:

Transaction Code:

Generally, a transaction is an operation that lets a user make changes to a database. The overall R/3 system must be seen as a business transaction processing system. This means that the whole data flow that runs across application modules is executed using transactions.

The transactions usually contain two phases: an interactive phase and an update phase.

All the transactions in the R/3 system have an associated transaction code. The available transaction codes are held in table TSTC. We can see this by using tcode SE93 or by using transaction SE16 (Data Browser) and entering the table name in the input field.

Generally, a transaction is an operation that lets a user make changes to a database. The overall R/3 system must be seen as a business transaction processing system. This means that the whole data flow that runs across application modules is executed using transactions.

The transactions usually contain two phases: an interactive phase and an update phase.

All the transactions in the R/3 system have an associated transaction code. The available transaction codes are held in table TSTC. We can see this by using tcode SE93 or by using transaction SE16 (Data Browser) and entering the table name in the input field.

03. Basic Architectural Concepts

Basic Architectural Concepts

02. What is means by R/3

What is means by R/3

R/3 means three layers are installed in Different system/server and they are connected with each other.

01. Presentation Layer : This  is the layer form where end user works on sap system by using sap gui or web gui.

02. Application Layer : On this layer dispatcher distribute the work load to the different work processes like Dialog , background,  spool, update, and enqueue and makes the job done.

03. Database Layer : This is the layer where it contains three buffer  D/B buffer, SQL buffer and Redo log buffer and a Actual data base where the committed data is stored

SAP AG: The Company behind R/3

SAP AG was founded in 1972 by four former IBM employees. The company headquarters are based in Walldorf, a small German town.

The company name, SAP, stands for Systems, Applications and Products in Data Processing. After the introduction of SAP R/3 in 1992, SAP AG has become the world's leading vendor of standard application software.

R/3 Release

3.0 , 3.1 , 4.0 , 4.5 , 4.7E , ECC5 , ECC6 with EHP Packs.

01. Introduction

01. Introduction

What Is ERP

ERP is short for Enterprise Resource Planning.

Enterprise resource planning (ERP) is business process management software that allows an organization to use a system of integrated applications to manage the business and automate back office functions. ERP software integrates all facets of an operation, including product planning, development, manufacturing processes, sales and marketing.

ERP is a high-end sophisticated software solution that reduces the pressure and workload off the managers or top level management and provides accurate, timely information for taking appropriate business decisions. Managers with knowledge of ERP will be able to achieve their targets and goals by proper implementation of ERP system in their organization.

In fact managers are expected to translate the business rules and requirements for mapping them into ERP software.

Implementation of ERP solutions is one of the largest drivers of growth in the consultancy business

ERP companies in market

SAP, Oracle, Microsoft, BAAN, Peplesoft etc.