SHAIKH AKHTAR'S DBA BLOG

ORACLE 10G ARCHITECTURE

THE FOLLOWING VIDEO WILL HELP YOU IN UNDERSTANDING THE BASIC WORKING PRINCIPLE OF ORACLE 10g ARCHITECTURE

ORACLE 10G ARCHITECTURE

THE PREREQUISITES

Oracle 10g Architecture

THE ORACLE 10g SERVER IS SIMPLIFIED INTO 2 MAIN PARTS

1. LOGICAL STRUCTURE

2. PHYSICAL STRUCTURE

1.LOGICAL STRUCTURE

The logical structure is created on RAM.

It is called as "Instance" 

It is a gateway to the physical database.

Data is first loaded from the physical database to the RAM before being displayed to the user.

2.PHYSICAL STRUCTURE

The physical structure consists of the actual location at which all the data is physically located.

The data is stored on the HDD.

THE LOGICAL STRUCTURE (INSTANCE) CONSISTS OF 2 PARTS

1.1 MEMORY STRUCTURE

1.2 BACKGROUND PROCESS

THE MEMORY STRUCTURE IS FURTHER DIVIDED INTO 2 MAIN PARTS

1.1.1 SHARED GLOBAL AREA (SGA)

1.1.2 PROGRAMABLE GLOBAL AREA (PGA)

1.1.1 SHARED GLOBAL AREA (SGA)

THE SGA consists of 6 components of the oracle architecture (explanantion given below)

1.Shared pool.....................................................................................(Dynamic in nature)

2.Database buffer cache (DBC).............................................................(Dynamic in nature)

3.Online redo buffer cache (RBC)..........................................................(Static in nature)

4.Large pool........................................................................................(Dynamic in nature)

5.Java pool..........................................................................................(Dynamic in nature)

6.Stream pool......................................................................................(Dynamic in nature)

1.1.2PROGRAMMABLE GLOBAL AREA (PGA)

The PGA consists of the following.

1.Sorting Area

2.Private SQL area

3.Cursor State

4.Session ID

1.2 BACKGROUND PROCESS

The following are the necessary background processes required in an oracle 10g architecture.

1.Log Writer .....................(LGWR)

2.Database Writer..............(DBWR)

3.Checkpointer...................(CKPT)

4.System Monitor...............(SMON)

5.Process Monitor..............(PMON)

2. PHYSICAL STRUCTURE

THE PHYSICAL STRUCTURE CONSISTS OF TWO TYPES OF FILES

2.1 DATABASE FILES

2.2 NON-DATABASE FILES

2.1 DATABASE FILES

The database files are the most important files of the database.The database files actually run the database.If any one of the database files gets deleted/lost/corrupted, the production database will immediately go down (The database would stop functioning)

The following are the database files.

1.Control files

2.Data files

3.Online redo log files.

2.2 NON DATABASE FILES

The non database files are those files which help in the proper functioning of the database. If any one of the non database files gets deleted/lost/corrupted, the production database remains unaffected.

The following are the non database files

1.Parameter file

2.Password file

3.Archieve log file

4.Trace file

5.Backup file 

6.Archieve log file

7.Network file etc

HOW IT WORKS (STEP BY STEP)

STEP 1.

Whenever a user opens a software like Isqlplus etc.. (Client side), a user process is created.
Once the user process has been created, the user can enter the username, password and the database identifier (the name of the database to which the user wishes to connect).

STEP 2.

The username, password and the database identifier entered by the user are then checked.

Once a successful login takes place, a server process is created.

The server process will check the authenticity of the user.

The server process gets the details of the user from the Data Dictionary Cache (DBC).

The server process checks the details of the user like 

    What privileges does the user have on the database?

    Which schema can the user access?

    and so on...

STEP 3.

Once the authentication process completes,the user can now start writing SQL, PL/SQL statements on the editor screen at the client side. All these statements are stored in the library cache which is in the shared pool.PARSING is also done in the library cache.

PARSING consists of the following 4 parts






will publish more info soon..