What is control file and what is use of control file?

What is control file and what is use of control file?

Control file(small binary file) contains database name,CRD files locations(database structure),DB creation time-stamp, check point information and RMAN recent backup details. It is also used in database recovery.

When an oracle instance is started control file will be read during mount stage.

SQL> SHOW PARAMETERS control_files

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

control_files                        string      +DATA/pavandb/controlfile/control01.ctl

It is suggested to multiplex the control file in different locations

Controls file multiplexing:

sql>Shut immediate

Set the new location in pfile

control_files='+DATA1/PRODDB/CONTROLFILE/control01.ctl', '+DATA2/pavandb/controlfile/control02.ctl'

sql>alter database mount

sql>alter database open;

SQL> SHOW PARAMETERS control_files

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

control_files                        string      +DATA1/pavandb/controlfile/control01.ctl, +DATA2/pavandb/controlfile/control02.ctl

We can keep maximum of 8 controls files for a database. We can’t multiplex further.

                                                                                                             

We can read the control file after saving it in a location. This will be in human readable text format.

ALTER DATABASE BACKUP CONTROLFILE TO TRACE AS '/tmp/control_trace.sql'

click here to understand control file parameters using database creation script.