Even on the latest Oracle Engineered Systems like ODA X6-2S/M there’s only one single controlfile created by default. Despite the storage redundancy there’s always a risk of someone accidentally deleting a file or some logical corruption of the file.
Therefore, we always multiplex the controlfiles and online redo logs. But, what is the easiest way of adding a second controlfile to a database using OMF on a file system?

I think it’s the following procedure. Although, I’m gladly proven wrong with a even more elegant solution.

The command output has been stripped to the relevant information.

$ . oraenv
ORACLE_SID = [DUMMY] ? DEV1

$ rman target /


-- see, there is only one online log destination
RMAN> select name, value from v$parameter where name like 'db_create_online_log_dest_%';

NAME                                   VALUE
-------------------------------------- --------------------------------------
db_create_online_log_dest_1            /u03/app/oracle/redo/
db_create_online_log_dest_2
db_create_online_log_dest_3
db_create_online_log_dest_4
db_create_online_log_dest_5


-- set a second online log destination
RMAN> alter system set db_create_online_log_dest_2 = '/u02/app/oracle/oradata/DEV1' scope=both;


-- get the current controlfile path for later reference in commands
RMAN> select value from v$parameter where name = 'control_files';

VALUE
--------------------------------------------------------------------------------
/u03/app/oracle/redo/DEV1/controlfile/o1_mf_cwxjo46k_.ctl


-- this will make RMAN "restore" command create new controlfiles in all online log destinations
RMAN> alter system reset control_files;


-- restart instance so parameter changes will take effect
RMAN> shutdown immediate


-- only start in NOMOUNT as to be able to restore controlfile
RMAN> startup nomount


-- this will create two new OMF controlfiles based on existing one
--   remember, we have reset control_files parameter
RMAN> restore controlfile from '/u03/app/oracle/redo/DEV1/controlfile/o1_mf_cwxjo46k_.ctl';
...
channel ORA_DISK_1: copied control file copy
output file name=/u03/app/oracle/redo/DEV1/controlfile/o1_mf_cxf4q747_.ctl
output file name=/u02/app/oracle/oradata/DEV1/DEV1/controlfile/o1_mf_cxf4q74v_.ctl
Finished restore at 12-SEP-16


-- use the two newly created controlfiles at next startup
RMAN> alter system set control_files = '/u03/app/oracle/redo/DEV1/controlfile/o1_mf_cxf4q747_.ctl','/u02/app/oracle/oradata/DEV1/DEV1/controlfile/o1_mf_cxf4q74v_.ctl' scope=spfile;


-- the old controlfile is not needed anymore
RMAN> host "rm /u03/app/oracle/redo/DEV1/controlfile/o1_mf_cwxjo46k_.ctl";

RMAN> startup force

Since I’m using Oracle 12c RMAN is capable of running SQL just like this…no need to change between SQL*Plus and RMAN anymore.

(Please don’t debate the file system structure, it’s from an engineered system. I think it’s horrible!)