Oracle Database Admin (DBA) Tutorial: Control Files Management

1.  What is a control file?

A control file is a small binary file that records the physical structure of the database and includes:

•       The database name

•       Database Id

•       Database creation date

•       Names and locations of associated datafiles and online redo log files

•       Current archive log mode

•       The timestamp of the database creation

•       The current log sequence number

•       Checkpoint information

•       RMAN backup details

2.  Control file Multiplexing

Below are the steps to multiplex the control files

1. Shutdown the database
2. Copy an existing control file to new location using operating system commands (i.e. cp)
3. Edit the control_files parameter and set the new file name in the parameter file
4. Start the database

3.  Taking the backup of control file

Ex:

alter database backup controlfile to trace;

•       The control file trace will be generated under diagnostic_dest.

•       We can use the contents of this trace file to recreate the control files and rename the database.

Ex:-

Alter database backup controlfile to trace as ‘/u01/app/control.trc’;

Example control file created script in the trace file as:

STARTUP NOMOUNT

CREATE CONTROLFILE REUSE DATABASE "orcl" NORESETLOGS NOARCHIVELOG

    MAXLOGFILES 32

    MAXLOGMEMBERS 2

    MAXDATAFILES 32

    MAXINSTANCES 1

    MAXLOGHISTORY 449

LOGFILE

  GROUP 1 '/u01/app/oracle/t_log1.f'  SIZE 500K,

  GROUP 2 '/u01/app/oracle/t_log2.f'  SIZE 500K

# STANDBY LOGFILE

DATAFILE

  '/u01/app/oracle/t_db1.f',

  '/u01/app/oracle/dbu19i.dbf',

  '/u01/app/oracle/tbs_11.dbf',

  '/u01/app/oracle/smundo.dbf',

  '/u01/app/oracle/orcl.dbf'

CHARACTER SET WE8DEC

;

NORESETLOGS option: - use this only if the current versions of all online logs are available

RESETLOGS option: - Use this only if online logs are damaged