Error
PRCD-1084 : Failed to start service stby_db
PRCR-1079 : Failed to start resource ora.sbyORCL.stby_db.svc
CRS-5017: The resource action “ora.sbyORCL.stby_db.svc start” encountered the following error:
ORA-44317: database open read-only
ORA-06512: at “SYS.DBMS_SERVICE”, line 478
ORA-06512: at “SYS.DBMS_SERVICE”, line 229
ORA-06512: at line 1

Cause
Standby database is read-only.

Solution
1. Start the service on primary instead:

PRIM$ srvctl start service -d oraORCL -s stby_db


2. Run the Log switched command on Primary and shipped to Standby.

-- On Primary
SQL> alter system switch logfile;


3. Start the service on standby:

STANDBY$ srvctl start service -d sbyORCL -s stby_db


4. Stop the service on primary:

PRIM$ srvctl stop service -d oraORCL -s stby_db