Restoring and managing Control file in oracle

[Lachlann]

Hi All,

For my oracle database server,I need to restore my control file from the backup which is taken by RMAN. My database which is running very smoothly and suddenly it fails because of control file corruptions. How would I restore it back.would you give me some suggestion except the RMAN restoration procedure. I would be highly great full to follow your suggestion.

Thanks

[Praetor]

The Control file in oracle database :

The control file is the core point of Oracle database.It is a small binary file that contains the physical structure of the database.It contains some valuable information about the database through which the database controlled.

The primary records are as follows:

• Name of the database.
• Names and locations of datafiles and online redo log files.
• Records timestamp of the database creation.
• Contains current log sequence number.
• Database checkpoint information

[Katty]

Multiplex Control Files :

The control file is created automatically whenever you create the database and only one control file can be used to operate the database which is associated with the database during creation.If you are creating the database using DBCA(Database Configuration Assistance),database automatically creates three control files which have same information but it is just for security purpose.

You can run with your database with more than three control files using following strategy :
1- Change the parameter with the CONTROL_FILES parameter and add more locations where do you want to store the control files.
2- SHUT IMMEDIATE your database and open the folder where your control files are physically stored.
3- Copy the control file and paste on added locations with different names.
4- start your database with STARTUP and fire the SHOW PARAMETER command to make sure the existence of files .

[kelfro]

Backing up Control file :

You can backup your control files using ALTER command within two options :

1- Backup your control in a binary file which takes the .BKP extension.It is also the duplicate of existing control file.

SQL> ALTER DATABASE BACKUP CONTROLFILE TO '/oracle/backup/control.bkp';

2- This option creates a script to create a new control file which can be used later.

SQL> ALTER DATABASE BACKUP CONTROLFILE TO TRACE;

[Zecho]

Manage the Size of Control Files :

You can increase the size of the control files using the parameter which is declared during creation of database.you can change the values of parameters to increase and decrease the size of these files.The parameters are given below:

• MAXDATAFILES
• MAXLOGFILES
• MAXLOGMEMBERS
• MAXLOGHISTORY
• MAXINSTANCES

These parameters are being used to decrease and increase the size of control files.

[Reegan]

Restoring the Control file :

You can restore the control file if you don't want to use the RMAN method of restoration of control files using user managed method which will be as:

1- shut down your database
2- Copy the control file from backup or from another location and paste to replace the corrupted file and rename if your source file name is different
3- Start your database in mount stage and then divert to open stage.

To use another method,you should use to script method.Execute the contents of script and a new control file would be created.