Removing a control file

To remove a control file, we have to first identify the control file that caused the problem and modify the CONTROL_FILES parameter with  ALTER SYSTEM  SQL statement.

Example:

SQL> conn sys/orcl@to_primary as sysdba
Connected.

---- shutdown the database and intentionally remove 'control01.ctl' control file
SQL> shutdown immediate;
ORA-01507: database not mounted
  ORACLE instance shut down.

--- And then startup
SQL> startup;
ORACLE instance started.
 Total System Global Area 2499805184 bytes
Fixed Size                  8749920 bytes
Variable Size             687869088 bytes
Database Buffers         1795162112 bytes
Redo Buffers                8024064 bytes
ORA-00205: error in identifying control file, check alert log for more info

---- Check the control_files parameter values
SQL> show parameter control_files;
 NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
control_files                        string      D:\APP\ADMIN\VIRTUAL\ORADATA\O
                                                 RCL\CONTROL01.CTL, D:\APP\ADMI
                                                 N\VIRTUAL\FAST_RECOVERY_AREA\O
                                                 RCL\CONTROL02.CTL

---- The control01.ctl is removed intentionally as I explained it above, and set the control_files parameter to only 'control02.ctl'.
SQL> alter system set control_files='D:\app\Admin\virtual\fast_recovery_area\orcl\CONTROL02.CTL' scope=spfile;
 System altered.

----- Now shutdown the database to see the effect
SQL> shutdown immediate;
ORA-01507: database not mounted
  ORACLE instance shut down.

----Startup the database and it should open.
SQL> startup;
ORACLE instance started.
 Total System Global Area 2499805184 bytes
Fixed Size                  8749920 bytes
Variable Size             687869088 bytes
Database Buffers         1795162112 bytes
Redo Buffers                8024064 bytes
Database mounted.
Database opened.
SQL>