Oracle Architecture-Basic Concepts

Oracle Architecture

Oracle architecture is mainly used to analyze the composition, working process and principle of the database, as well as the organization and management mechanism of the data in the database.

Oracle Database

The Oracle database is a logical concept, not a server that is physically conceptually installed on the Oracle database management system.

Instance

An instance is a set of Oracle background processes and shared memory regions that are allocated on the server

Database

A database refers to a collection of physical files, such as disk-based data files, control files, log files, parameter files, and archive log files.

Database server

Database server refers to a variety of software tools (such as Sqlplus, OEMs, etc.) that manage the database, as well as 3 parts of an instance and database

The relationship between an instance and a database

Instance (a set of processes and shared memory) for managing databases (physical files);

The database provides data for the instance;

A database can be loaded and opened by multiple instances;

An instance can only mount and open a database during its lifetime.

Storage structure

The function of the database is to store the data, and the way the database stores the data is called the storage structure;

The storage structure of Oracle is divided into physical storage structure and logical storage structure.

Logical storage structure analyzes the composition of the database from the logical point of view, it is the logical concept partition of the data storage structure, which is used to describe the way of organizing and managing data in Oracle.

The physical storage structure is used to demonstrate the composition of the physical files of Oracle in the operating system.

Start the Oracle database server

Create an Oracle instance (a set of process + shared memory) in memory on the server and use this instance to access and control the database on disk (physical data files)

CS Communication Essence for Oracle Services

When a client (user) connects to a database, it is actually connected to an instance of the database, and the instance is responsible for communicating with the database;

SQL commands are sent from the client to the Oracle server, and the instance process responds;

parsing, compiling and executing in memory;

Writes the modified data to the data file, writes the modification information to the log file;

Finally returns the processing result to the client (user)

Oracle Architecture-Basic Concepts