Oracle Database Architecture

Oracle Server (server) by Oracle instance (instance) and Oracle database (database) composition.

1 Oracle database is made up of data files, control files, redo log file (redo logfile), parameter Files (initialization spfile and pfile), password file (password file), archived log files (archive log file), and so on. 、

2 The Oracle Instance (instance) consists of a database system global area (SGA) and various background processes for the database.

The SGA includes shared pood (Shared pool), Dabatase buffer cache (Database cache), Java Pood (Java pool), redo log buffer (redo log buffers), large pood (large pool).

3 Oracle's background process includes the PMNO (Process Monitor, progress monitoring process), SMNO (System Monitor, systems monitoring process), DBWR (database writer, db write process), LGWR (log writer, redo log write process), CKPT (check point, checkpoint process).

Oracle DBA Efficient onboarding Guide, page 376, is shown in Figure 19-1.

To set environment variables for an Oracle database:

Sql>set ORACLE_SID=ORCL

Or

Sql>export ORACLE_SID=ORCL

View the background process for Oracle databases under Linux:

$ps-ef|grep Ora_

Oracle logical Structure of a database:an Oracle database consists of one or more tablespace (tablespaces)---> Each tablespace contains multiple or one segment (segments)----> Each segment (segment) contains one or more extent (zones)----> each extent (Zone) contains one or more blocks.

Oracle's Tablespace (table space) consists of one or more data files.

View data files for the table space of the Oracle database: Dba_data_files data dictionary table

Sql>select file_name,tablespace_name from Dba_data_files;

See which segment data segments are included in the Users table space: dba_segments

Sql>select segment_name,tablespace_name from Dba_segments where tablespace_name

= ' USERS ';

See how many extent (zones) are in the EMP table: dba_extents

Sql>select owner,segment_name,tablespace_name,extent_id

From dba_extents where segment_name= ' EMP ';

To view the type of table space per database: Dba_tablespaces

Sql>select tablespace_name,contents from Dba_tablespaces;

Table Space Type:

Permanent: Permanent Table space

Undo: History Table Space

Temoorary: Temporary table space

A few important table spaces:

System tablespace: Contains basic information about a database run, such as a data dictionary table

Temp tablespace: Data is temporarily stored, and data is not persisted.

Users table space: Data is typically stored for database users.

Oracle Database Architecture