Control file and its functions in Oracle.

Control file and its functions in Oracle

This article answers the following queries :
•         What is the control file in oracle?
•         What are the functions of control file in oracle?
•         What are the control file contents ?
•         Can database function properly without control file?
•         Can we edit control file
•         Who can modify control file?
•         At what time control file will be created?

What is control file in Oracle and what are its functions ?
Control file is a small binary file which is necessary for the database to start and operate successfully.

What are the functions of control file ?
Each control file is associated with only one database.  Oracle continuously updates control file during database use so this file must be available for writing whenever the database is in the open state.  Control file will be created at the same time of database creation.
Whenever a datafile or a redolog file is added to, dropped or renamed in the database, the control file is updated to reflect the physical structural change.
These changes are recorded in control file which facilitates:
>   Oracle to identify the files that are required or available in case database recovery is needed
>   Oracle to identify the datafiles and redolog files to open during database startup.

Can database function properly without control file?
No. Database cannot function properly if the control file is not available.

Can we edit control file? Who can modify control file?
Please note control file cannot be edited by database administrator or by any user. Control file information can only be modified by Oracle.

Contents of control files :
> Control file contains information such as
>   Database name
>   Timestamp of database creation
>   Tablespace information
>   The log history
>   Archive log information
>   Current log sequence number
>   Checkpoint information
>   Names and locations of associated datafiles and redolog files
>   Datafile copy information
>   Datafile offline ranges
>   Backup set and backup related information
>   Backup datafile and redolog information

BRBACKUP/BRARCHIVE failed, warning ORA-28011: the account will expire soon; change your password now.

New LIMIT for ‘PASSWORD_LIFE_TIME’ in Oracle 11g.

One of my colleague go through this solution.  Hope this helps you.

Some thing new in 11g, If you are using please rectify.

Any user in Oracle 11g using DEFAULT profile, has a default limit for PASSWORD_LIFE_TIME is 180 days, then that will be in GRACE period (Will never expire.)
So after 180 days it will throw the Warning ORA-28011: the account will expire soon; change your password now.
As a part of this if backups or jobs are scheduled from those user IDs, will start failing after 180 days.
Note: Prior to Oracle Database 11g Release 2 (11.2), the default was UNLIMITED. Ref SAP Note 1519872
Script to find out the same is,
select LIMIT, RESOURCE_NAME from dba_profiles where  PROFILE = ‘DEFAULT’ and  RESOURCE_NAME in (‘PASSWORD_GRACE_TIME’,’PASSWORD_LIFE_TIME’);
Remedy is,
ALTER PROFILE DEFAULT LIMIT PASSWORD_LIFE_TIME UNLIMITED;