Oracle Server Architecture

Primary components:

1)      Oracle server: Consists of Oracle Instance and oracle physical file structure that we will discuss next.

2)      Oracle Instance: Consists of the background processes and memory structures.

 When you connect to any database it allocates a memory area called System Global Area (SGA).

And mandatory background process PMON, SMON, DBWR, LGWR, CKPT also starts. Background process performs automatic read/write operations from physical file to SGA component & vice versa and managing memory. Thus one instance can connect to only one database.

3)      Oracle Database : Consists of files organization required for physical storage of data, backup files of database and other information required at the time of recovery in case of instance failure.

Following types of physical file present.

•       Pfile :  parameter file is a text file contains initialization parameters needed to startup database.
•       Spfile:  server parameter file it is a binary file containing  initialization parameters needed to startup database.
•       Control file:  contains information about physical location of other files.
•       Redo log file: contains log entries of each activities in database. Used for recovery of database.
•       Archive log file: it is back up of redo log files when redo log files are full.
•       Data file: Actual schema and data is stored here.
•       Alert log files: Text file where all major database activities are recorded with timestamp.
•       Trace log files: contains the details of error generated from system, server or by users.
•       Password file:  Specifies the authentication of database users.

File type	Extension	Default  location (when created with OMF)
Pfile :	ORA	C:\oracle\product\10.2.0\admin\orcl\pfile
Spfile:	ORA	C:\oracle\product\10.2.0\db_1\database
Control file:	CTL	C:\oracle\product\10.2.0\oradata\orcl
Redo log file:	LOG	C:\oracle\product\10.2.0\oradata\orcl
Archive log file:	LOG	C:\oracle\product\10.2.0\flash_recovery_area\ORCL\ARCHIVELOG
Data file:	DBF	C:\oracle\product\10.2.0\oradata\orcl
Alert log files:	LOG	C:\oracle\product\10.2.0\admin\orcl\adump
Trace log files:	TRC	C:\oracle\product\10.2.0\admin\orcl\udump|bdump|cdump
Password file:	ORA	C:\oracle\product\10.2.0\db_1\database

 

In my next post I will discuss use of all SGA components shown in figure and roles of all the background processes.