Physically Oracle DB is seen as a collection DB files. The initial Database is collection of 10 to 12 files. If this storage is not sufficient then DBA can add more files to the Database.
All these files are categorized into 3 types
1. Data files (5 or 6)
2. Control files (2 or 3)
3. Online redo log files (3)
DATAFILES:-
These files are used to store Data in the form of tables. The files are created with extension .dbf
All these files are categorized into 3 types
1. Data files (5 or 6)
2. Control files (2 or 3)
3. Online redo log files (3)
DATAFILES:-
These files are used to store Data in the form of tables. The files are created with extension .dbf
Oracle DB is created with 5 or 6 data files initially.
1. system01.dbf
2. sysaux01.dbf
3. undotbs1.dbf
4. users01.dbf
5. temp01.dbf
6. example01.dbf (optional)
2. sysaux01.dbf
3. undotbs1.dbf
4. users01.dbf
5. temp01.dbf
6. example01.dbf (optional)
System01.dbf:-
It is the master file of Oracle DB. It maintains “Data dictionary”. This is only one mandatory file. It is default storage for DBA users (SYS , SYSTEM).
It is the master file of Oracle DB. It maintains “Data dictionary”. This is only one mandatory file. It is default storage for DBA users (SYS , SYSTEM).
Sysaux01.dbf:-
It is introduced in Oracle 10g. It acts as an extension to system01.dbf.
It is for the following features
1.Maintains Oracle Enterprise Manager (EM) Repository.
2.Support for Oracle xml
3.Support for Data Warehousing
4.Support for Oracle Intermedia (Multimedia)
5.Support for special (multidimensional)
6.Support for Oracle Text search
It is introduced in Oracle 10g. It acts as an extension to system01.dbf.
It is for the following features
1.Maintains Oracle Enterprise Manager (EM) Repository.
2.Support for Oracle xml
3.Support for Data Warehousing
4.Support for Oracle Intermedia (Multimedia)
5.Support for special (multidimensional)
6.Support for Oracle Text search
Undotbs01.dbf:-
It is used to maintain data related to the running transactions until transaction is finalized.
It is used to maintain data related to the running transactions until transaction is finalized.
Users01.dbf:-
It is the default storage for normal users such as Scott.
It is the default storage for normal users such as Scott.
Temp01.dbf:-
It is to arrange the data in proper order during execution of a command. It is preferably used if the data is more than 64 KB.
It is to arrange the data in proper order during execution of a command. It is preferably used if the data is more than 64 KB.
Example01.dbf:-
It maintains data for learning purpose in other words it acts a demo example application. These applications are used by H.R users.
It maintains data for learning purpose in other words it acts a demo example application. These applications are used by H.R users.
CONTROL FILES:-
It is binary file used to maintain key important details of Oracle database Such as
DB Name
DB Creation date and time
DB files details
State of DB
Backup details of DB etc.
Oracle DB server uses the above details of control files to recognize, open and operate the database. If ever the control file is Damaged Oracle DB server can’t handle the Database.
For safety purpose generally Oracle server is created with multiple copies of control files called multiplexing control files.
Note:- for creating and operating Oracle DB one control file is mandatory.
It is binary file used to maintain key important details of Oracle database Such as
DB Name
DB Creation date and time
DB files details
State of DB
Backup details of DB etc.
Oracle DB server uses the above details of control files to recognize, open and operate the database. If ever the control file is Damaged Oracle DB server can’t handle the Database.
For safety purpose generally Oracle server is created with multiple copies of control files called multiplexing control files.
Note:- for creating and operating Oracle DB one control file is mandatory.
ONLINE REDOLOG FILES:-
These files are used to maintain details of Oracle DB operations as a duplicate copy. As usual the original details are stored permanently in data files. So in other words online backup of database maintain in online redo log files. These details are stored in the form of an entry called redolog entry.
These files are used to maintain details of Oracle DB operations as a duplicate copy. As usual the original details are stored permanently in data files. So in other words online backup of database maintain in online redo log files. These details are stored in the form of an entry called redolog entry.
These redo log entries are used to repair the damaged data files. By default Oracle database is created with 3 online redolog files as members in 3 redolog groups.
Oracle DB server starts writing redo entries in redolog files, whenever database operation is performed. If ever redolog file is filled then Oracle DB server performs log switching. So that DB server start using next available redolog file for writing redo entries.
Once all redolog files are used, then DB server starts writing redo entries. Before this happens it is necessary to perform any one the following two operations.
1. Taking Backup of Oracle DB.
2. Taking backup of filled redolog file.
1. Taking Backup of Oracle DB.
2. Taking backup of filled redolog file.
Note:- In order to create and maintain Oracle DB two redolog groups are mandatory.
Conclusion: In order to create Oracle DB the following minimum no.of files are needed. They are
Data files : system01.dbf
……………..: sysaux01.dbf
Control files: control01.ctl
Online redolog files : redo01.log
………………………….: redo02.log
Data files : system01.dbf
……………..: sysaux01.dbf
Control files: control01.ctl
Online redolog files : redo01.log
………………………….: redo02.log
EXPLORING PHYSICAL ARCHITECTURE OF ORACLE DATABASE
Oracle DBA users such as SYS or SYSTEM can use Physical Architecture of Oracle Database
Obtaining details of permanent Data files
Obtaining details of temporary content Data files
Obtaining details of control files
Obtaining details of online redolog groups
Obtaining details of redolog members
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