Here we will discuss about what is SAP instance and SID

What is an Instance?

There are three types of instances:-

  1. Dialog instance
  2. Central Instance
  3. Database Instance

Sap Instance is a group of resources such as

  • Memory
  • Work Processes
  • Dispatcher
  • Gateway

usually for a single application or database server within a SAP R/3 client-server environment.

When you install an SAP system, three SAP instances will be created. They are

  • Dialog Instance: – We can have more no of Dialog instance for one SAP system. This will help us to distribute the load of SAP system. Dialog instance exists in the application layer. Its purpose is to maintain the load on the server. Dialog instance exists on the different host. If a number of dialog instance increases hardware resources, dispatcher, workprocesses also increases so that more number of users can login at a time.
  • Central Instance: – There will be only one instance for one SAP system. The identification of central and dialog instance will be an Enqueue process. Only Central instance will be having the Enqueue process. Central instance can also work as dialog instance. But the main thing is that it contains Enqueue and message servers. All dialog instances communicate with central instance before requesting  database with message server. When an instance is started, the dispatcher process attempts to establish a connection to the message server so that it can announce the services it provides (DIA, BTC, SPO, UPD, etc.).Lock table is managed in central instance by enqueue service.
  • Database Instance: – As normal database instance accepts requests from central instance to fulfill the user’s requests. As lock management system provided by enqueue server, it will provide service to users.

What is  SID?

SID is a unique identification code for every R/3 installation (SAP system) consisting of a database server & several application servers. SID stands for SAP System Identification. SAPSID — a three-character code such as C11, PRD, E56, etc.)

Naming standards for SID:


SID Description – P=Production(type) , B=BW(component) , G=Germany.(plant name)

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