Components of the oracle8i-system Architecture (introductory article)

Oracle
In this article you will learn the following:

Can describe the system structure of the Oracle8i server and its main components.



ORACLE8I system structure as shown in the following figure, I believe that we are very familiar with this map:











Oracle8i is an object-oriented relational database management system, and the following is an introduction to its main components:

1. Oracle Instance (Oracle instance)

An Oracle instance is composed of a set of background processes and memory regions. The instance must be started in order to be able to access the data. Each instance starts with the allocation of the system Global Are (SGA) and the start of the background process.

The SGA consists of the following parts

Share Pool (including dictionary buffer SQL statement buffer)

Data buffer Cache (first written to the buffer when changing the contents of the database)

Redo Log buffer (saved to the buffer before the redo log is written to the physical file)

Background processes that must be started in Oracle8i have

The DBWR (data write process) writes the data in the changed buffer to the data file.

The LGWR (log write process) writes the data in the redo log buffer to the redo log file.

Smon (System monitoring process) such as automatic recovery when database is started

Pmon (Process monitoring process) If an Oracle process fails, the Pmon process clears the process

Resources that are occupied.

CKPT (checkpoint process) changes the database control file. (as I understand it)

2. Database files

A database file is an operating system file that stores database data.

3. Other documents

Include parameter file, redo log file, archive log file, control file, password file, etc. Only the database generates an archive log file in archive mode.