STORAGE STRUCTURE

DATABASE STORAGE STRUCTURE:

The database is just a set of files present on disk. These files are created when we create the Database using the 'CREATE DATABASE' statement.

When looking at server level, we may find the files as .log .trc .trm .dbf .ctl. Oracle uses the logical structure to organize the files internally.

The data dictionary maintains the relationship between the physical and logical structure

I) Physical Database Structure:

CONTROL FILES

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')