Dedicated to an old friend and colleague.
1. Add the service. Please take note, the instance names are in UPPER case.
[oowner@gxtbdb01 ~]$ srvctl status service -d utldb
[oowner@gxtbdb01 ~]$ srvctl add service -d utldb -s test -r UTLDB1
2. Start it
[oowner@gxtbdb01 ~]$ srvctl status service -d utldb
Service test is not running.
[oowner@gxtbdb01 ~]$ srvctl start service -d utldb -s test
[oowner@gxtbdb01 ~]$ srvctl status service -d utldb
Service test is running on instance(s) UTLDB1
3. Modify it to add a new instance to the preferred list
[oowner@gxtbdb01 ~]$ srvctl modify service -d utldb -s test -n -i UTLDB1,UTLDB2
[oowner@gxtbdb01 ~]$ srvctl status service -d utldb
Service test is running on instance(s) UTLDB1
4. Service has to be restarted for the changes to take into effect
[oowner@gxtbdb01 ~]$ srvctl stop service -d utldb -s test
[oowner@gxtbdb01 ~]$ srvctl start service -d utldb -s test
[oowner@gxtbdb01 ~]$ srvctl status service -d utldb
Service test is running on instance(s) UTLDB1,UTLDB2
Cheers!
Maaz Anjum's Blog 