ORACLE DATBASE ARCHITECTURE

Many materials and websites offer a different to the same Oracle Architecture. Therefore one is left confused after reading several sources. Therefore I have made an effort to pool in all the info into an understandable form. Lets see what lies beneath the giant Oracle.



Oracle database consists of 2 types:

1) Database

2) Instance



1) Database:

The database is the physical files on disk. This consists of 2 parts:

I) Physical Database Structure

II) Logical Database Structure





I) Physical Database Structure:



The Physical Database structure conists of:

i) Datafiles

ii) Control Files

iii) Redo Log Files

iv) Other files like Server Parameter files, Alert Log Files, Trace Files



II) Logical Database Structure:



The Logical Database Structure consists of:

i) Data Blocks

ii) Extents

iii) Segments

iv) Tablespaces



2) Instance:

Instance consists of:



I) Memory Structures

II) Background Processes (or just 'Processes')

ORACLE DATBASE ARCHITECTURE

Many materials and websites offer a different to the same Oracle Architecture. Therefore one is left confused after reading several sources. Therefore I have made an effort to pool in all the info into an understandable form. Lets see what lies beneath the giant Oracle.

Oracle database consists of 2 types:
1) Database
2) Instance

1) Database:
The database is the physical files on disk. This consists of 2 parts:
I) Physical Database Structure
II) Logical Database Structure


I) Physical Database Structure:

The Physical Database structure conists of:
i) Datafiles: contains all database data which is stored logically in the form of tables and indexes
ii) Control Files: contains metadata about the physical structure of the database and details about the database and the database files
iii) Redo Log Files: records all changes made to data
iv) Other files like Server Parameter files, Alert Log Files, Trace Files



II) Logical Database Structure:

The Logical Database Structure consists of:
i) Data Blocks: lowest level of storage structure. Each data block contains a specific number of bytes on  disk
ii) Extents: contains contiguous data blocks and is used to store specific information.
iii) Segments: is a set of extents. It is used for storing database objects.
iv) Tablespaces: contains logical segments. Physically it contais atleast one datafile. Data is stored logic in a tablespace but physically in  datafiles.

2) Instance:
Instance consists of:

I) Memory Structures
II) Background Processes (or just 'Processes')