Error in dataguard alert log/start managed recovery process:-

SYS@XXX>alter database recover managed standby database;
alter database recover managed standby database
*
ERROR at line 1:
ORA-00283: recovery session canceled due to errors
ORA-01111: name for data file 61 is unknown – rename to correct file
ORA-01110: data file 61: ‘/u01/app/oracle/product/12.1.0/db_1/dbs/UNNAMED00061’
ORA-01157: cannot identify/lock data file 61 – see DBWR trace file
ORA-01111: name for data file 61 is unknown – rename to correct file
ORA-01110: data file 61: ‘/u01/app/oracle/product/12.1.0/db_1/dbs/UNNAMED00061’

Solution:-

Check the exact size of the datafile in primary for file_id=61

In Standby,

SYS@XXX>alter system set standby_file_management=manual;

System altered.

SYS@XXX>Alter database create datafile ‘/u01/app/oracle/product/12.1.0/db_1/dbs/UNNAMED00061’ as ‘+DATA/’ size 34358689792;

Database altered.

SYS@XXX>alter system set standby_file_management=auto;

System altered.

Now you will be able to start managed recover process.