SAP stands for Systeme, Anwendungen, Produkte in der Datenverarbeitung -- which is German for “Systems, Applications and Products in Data Processing” -- and refers to a leading suite of business software. A SAP system consists of an essential part, known as a kernel, which is a collection of executable programs that allow the system to function, and a number of subsystems. All of the kernel programs started or stopped together are known as a "SAP instance," while each subsystem within an instance is known as a "SAP client."\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t \t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tSAP Instance
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The term “instance” -- often used interchangeably with “server” or “application server” -- typically refers to one occurrence of the SAP runtime software running on a single server platform. However, SAP instances are defined during the installation process, so it may be desirable to install multiple instances on a single server platform. In any case, each SAP instance consists of a group of resources, including memory, multiple work processes dedicated to specific work tasks and a single dispatcher, which distributes requests to those processes.
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A SAP instance typically has a three-character name, such as “DEV” or “PRD,” which corresponds to the purpose for which it is used. The data for each instance is contained in a separate database from other instances, so an instance named “PRD” -- short for “production” -- would indicate an instance intended for everyday production use, rather than development, testing, quality assurance or any other purpose.
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A SAP client can be thought of as a logical component, or subsystem, of a SAP instance, such that an instance can contain more than one client. A SAP client is typically represented by a three-digit number, which is used in combination with the name of the SAP instance of which the client is a component to create the client name. A production instance could contain just a single usable client, called “PRD100” or something similar, but other instances could contain multiple clients, depending on their exact purpose.
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The SAP system can be subdivided into application, database and presentation servers, but typically only the application and database servers are considered part of the SAP system proper. The presentation server -- often in the form of a graphical user interface (GUI) running on a user’s computer -- is sometimes referred to as a “client,” but is not, in fact, a SAP client in the true sense of the term.
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