Basis Architecture

Basis Architecture 

Sap system comprises of 3 different tiers:

1. SAP application tier.
2. SAP database tier.
3. SAP presentation tier.

1. SAP application tier addressed as central instance or dialog instance, where central and dialog instances have all the ability to process all the users requests, executed by the users from their GUI. The CI & dialog instance comprises of work processes and services which are responsible for processing users request.

2. SAP database tier of SAP system comprises of 4 major components.

-ABAP component
-BASIS component
-HR component
-LOGISTICS & ACCOUNT components (sd,mm,pp,fi etc)

These major components makes the SAP database and also gives helps to process the GUI.

3. SAP presentation tier has to be loaded on every desktops/laptops of an end-users, through which users can access SAP application and database.

Note:

- Any sap system is built upon a 3 tier architecture, where presentation layer is considered as a GUI.
- Central instance or dialog instances are considered as SAP application.

What is central instance architecture ?

Architecture of central instance is designed to process all the users request. They consist of work processes, services and a dispatcher.

- A dispatcher has the ability to accept the work from a user GUI, and trigger it to the right and free work process depending on the task executed by the user.

- Services of SAP system are responsible for communication via dedicated port numbers, where message service is responsible for communicating b/w SAP applications and central database.

- SAP applications context are: central and dialog instances.

- Message server port number is 3600

- Gateway service is responsible for communication b/w SAP to SAP and SAP to NON SAP systems via dedicated port numbers.

- Gateway server port number is 3300.

What is work process?

In any central instance of an R/3 system one can find 5 work processes, they are:

1. Dialog work process
2. Background work process
3. Update or V1/V2 work process
4. Spool work process
5. Enqueue work process

1. Dialog work process is responsible for on-line transactions, they are represented as "DIA".

2. Background work process is responsible for processing long-running or off-line tasks without a direct user interaction, they are represented as "BTC" or "BGD".

3. Update work process is responsible for saving the data in the database tables. There are 2 types of updates represented as "UPD" and "UP2". They can also be represented as synchronous and asynchronous V1/V2 again or critical and less critical respectively.

* UPD ---> synchronous ---> V1 ---> critical
* UP2 ---> asynchronous ---> V2 ---> less critical

4. Spool work process are represented as "SPO" and are responsible for printing in SAP system.

5. Enqueue work process is represented as "ENQ" and it is responsible for locking mechanism, ENQ prevents deadlocks over database tables, by processing user request in "Q"(fifo) fashion.

The central instance is represented as "DVEBMGS"

-DIALOG
-V2
-ENQUEUE
-BACKGROUND
-MESSAGE
-GATEWAY
-SPOOL