Oracle Database Architecture Overview

Oracle database system is a complex software system. Oracle architecture refers to the components of an Oracle database management system and the interrelationships between these components, including memory structure, background process, physical and logical structure, and so on.

The following figure is an Oracle database system master diagram:

The Oracle database system is complex and complex because it minimizes memory, and as you can see from the diagram above, it is divided into instances and database files in its entirety.

One, instance (Instance): Refers to the database server memory and related processing program, it is Oracle's heart. The most important relationship with Oracle performance is the SGA (System global area, which is the live shared memory area of the systems Globe), and the SGA contains three parts:

1, data buffer, can avoid repeatedly read the commonly used data;

2, the log buffer, improve the data deletion and modification speed, reduce disk read and write and speed up;

3, the shared pool, so that the same SQL statement no longer compile, improve the execution speed of SQL.

Second, the database file, by the operating system within the various file groups composed.

1. Oracle Database Logical Structure:

1. Table space, the basic logical structure of the database, is a series of data files collection;

2. Paragraph, different types of data in the database occupied by the space, there are many combinations of areas;

3). The purpose is to reserve a large space for the data at once;

4. block, the smallest storage unit, specified when creating the database.

2. The physical structure of Oracle database:

1. data file, file for storing data;

2. Redo log files (Redo log file), responsible for recording the processing of any data in the database, can be used for data recovery;

3. Control files, control and record the entity structure of the database;

4. Initialize the parameter file (initialization Parameter file), and configure the memory space basis;

5. password file (Password file), which authenticates the user's permissions to start and close Oracle routines.