Oracle7 Server Concepts
The Program Interface
The program interface is the software layer between a database application and Oracle. The program interface does the following:
- provides a security barrier, preventing destructive access to the SGA by client user processes
- acts as a communication mechanism, formatting information requests, passing data, and trapping and returning errors
- converts and translates data, particularly between different types of computers or to external user program datatypes
The Oracle code acts as a server, performing database tasks on behalf of an application (a client), such as fetching rows from data blocks. It consists of several parts, provided by both Oracle software and operating system-specific software.
Program Interface Structure
The program interface consists of the following pieces:
- various SQL*Net drivers (protocol-specific communications software)
- operating system communications software
Both the user and Oracle sides of the program interface execute Oracle software, as do the drivers.
SQL*Net is the portion of the program interface that allows the client application program and the Oracle Server to reside on separate computers in your communication network.
The Program Interface Drivers
Drivers are pieces of software that transport data, usually across a network. They perform operations like connect, disconnect, signal errors, and test for errors. Drivers are specific to a communications protocol. There is always a default driver.
You may install multiple drivers (such as the asynchronous or DECnet drivers), and select one as the default driver, but allow an individual user to use other drivers by specifying the desired driver at the time of connection. Different processes can use different drivers. A single process can have concurrent connections to a single database or to multiple databases (either local or remote) using different SQL*Net drivers.
The installation and configuration guide and SQL*Net documentation for your system contains details about choosing and installing drivers and adding new drivers after installation. The SQL*Net documentation describes selecting a driver at runtime while accessing Oracle.
Operating System Communications Software
The lowest level software connecting the user side to the Oracle side of the program interface is the communications software, which is provided by the host operating system. DECnet, TCP/IP, LU6.2, and ASYNC are examples.
Additional Information: The communication software may be supplied by Oracle Corporation but is usually purchased separately from the hardware vendor or a third party software supplier. See your Oracle operating system-specific documentation for more information about the communication software of your system.