Control Files & Database

(1)  When a database is created, at least one control file is also created. The control file MUST be available for writing by the Oracle server whenever the database is open. Without the control file, the database cannot be mounted. Thus, it is recommended that we multiplex control files on different disks and backup the control file for safety reason. 

(2) We can create a new control file as following...

CREATE CONTROLFILE SET DATABASE orcl 
LOGFILE GROUP 1 ('/u01/oracle/prod/redo01_01.log', '/u01/oracle/prod/redo01_02.log'), 
                 GROUP 2 ('/u01/oracle/prod/redo02_01.log', '/u01/oracle/prod/redo02_02.log'),
                 GROUP 3 ('/u01/oracle/prod/redo03_01.log', '/u01/oracle/prod/redo03_02.log') RESETLOGS
DATAFILE '/u01/oracle/prod/system01.dbf' SIZE 3M, 
                   '/u01/oracle/prod/rbs01.dbs' SIZE 5M, 
                   '/u01/oracle/prod/users01.dbs' SIZE 5M, 
                   '/u01/oracle/prod/temp01.dbs' SIZE 5M   
MAXLOGFILES  50  MAXLOGMEMBERS 3 MAXLOGHISTORY 400 
MAXDATAFILES 200 MAXINSTANCES 6 ARCHIVELOG;

 (3) We can display control file information using some views such as  v$database, v$controlfile, v$controlfile_record_section and v$parameter

(4) The control file locations and names are specified by  CONTROL_FILES parameter in the initialization parameter file.