What is Oracle Server Structure ?

Posted Date: 04-Aug-2011	Category: Computer Knowledge	Rating:
Author: Nilabh Raj	Member Level: Bronze	Points: 10 (Rs 2)

In this article I will give you a quick overview of the Oracle Server and the various physical files of the Oracle Server along with their function. This gives you a quick functionality of the Oracle Server physical structure

The Oracle Server
1)Oracle Server comprises of Oracle Database and Oracle Server Instance.
2)Oracle Database has got both physical and logical structures.
3)The physical part is the actual files, that are stored as Operating System files.
4)These include Data files, redo log files and control files.
5)There could be more than one file under each category.

Physical Components of the Database:
Data Files
Redo Log Files
Control Files

Data Files
1)These are the files that store the database's data.
2)They can be set to get extended automatically, when they run out of space.
3) More datafiles can also be added later.
4) Whenever the application requests data , Oracle reads the data from the datafile.
5) This will happen only if the data is not already present in the memory.
6) The data to be read from or written to the file, is first spooled in the memory.
7) It is written to the data files in one stroke when memory is full or according to a pre determined logic.
8) DBWR (Database Writer) process is responsible for this activity.

Redo Log Files
1) Redo log records ALL changes made to the data.
2) Please note that the data is first changed in the buffer cache.
3) Redo log is the very first file to be written to, by Oracle.
4) It is used in data recovery (both instance and media recovery) operations.
5) Media recovery will require the redo logs to be archived.
6) Normally multiple sets of redo log files are maintained across various disks.
7) This is called multiplexing and reduces single point dependency.

Control Files
1) Contain the following information specific to the particular database.
2) Database name.
3) Names and locations of the data files.
4) Names and locations of the redo log files.
5) Time Stamp of the Database creation.
6) Used during startup and recovery of the database.

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