Data Guard was configured a few days back at one of the customers site. An ORA-19527 error is continuously reported in the standby database alert.log (database name is changed)

Errors in file /u01/app/oracle/diag/rdbms/orcl/ORCL1/trace/ORCL1_rfs_3504.trc:
ORA-19527: physical standby redo log must be renamed
ORA-00312: online log 9 thread 1: '+DATAC1/ORCL/ONLINELOG/group_9.459.960055023'

Though this didn't stop the data guard replication, the customer wanted to get-rid the message. Starting with v10g, this was an expected behavior to improve the switchover and failover. With v10g, when MRP is started, it will attempt to clear the online log files.

This is also an expected behavior when the log_file_name_convert parameter is set on the standby database. But, in our case, the log_file_name_convert was not required as PRIMARY and STANDBY has the same directory structure (DISK GROUPS for DATA and RECO).

The workaround to get rid of the message, when there is no different in the directory structure, is just to set some dummy values to the parameter, as shown in the below example:

SQL> ALTER SYSTEM SET log_file_name_convert='dummy','dummy';

After the parameter was set, the ORA message was no longer seen in the alert.log

ORA-19527 reported in Standby Database when starting Managed Recovery (Doc ID 352879.1)
ORA-19527: Physical Standby Redo Log Must Be Renamed...during switchover (Doc ID 2194825.1)