ORA-01110: data file xx MRP0: Background Media Recovery process shutdown 

whilst doing a simple admin task we ran into issue on our production DG setup. On primary DB we ran out space on one Table space and as routine task one of our DBA, added data file on primary. Usually this kind of changes were routine in our env having DG setup, but in this particular setup we ran into the issue. 


Log file shows - 

MRP0: Background Media Recovery terminated with error 1111
Errors in file /u01/app/oracle/diag/rdbms/xxxxxxx/xxxxxxx/trace/xxxxxxx_pr00_22450.trc:
ORA-01111: name for data file 25 is unknown - rename to correct file
ORA-01110: data file 25: '/u01/app/oracle/product/11.2.0/db_1/dbs/UNNAMED00025'
ORA-01157: cannot identify/lock data file 25 - see DBWR trace file
ORA-01111: name for data file 25 is unknown - rename to correct file
ORA-01110: data file 25: '/u01/app/oracle/product/11.2.0/db_1/dbs/UNNAMED00025'
Slave exiting with ORA-1111 exception
Errors in file /u01/app/oracle/diag/rdbms/xxxxxxx/xxxxxxx/trace/xxxxxxx_pr00_22450.trc:
ORA-01111: name for data file 25 is unknown - rename to correct file
ORA-01110: data file 25: '/u01/app/oracle/product/11.2.0/db_1/dbs/UNNAMED00025'
ORA-01157: cannot identify/lock data file 25 - see DBWR trace file
ORA-01111: name for data file 25 is unknown - rename to correct file
ORA-01110: data file 25: '/u01/app/oracle/product/11.2.0/db_1/dbs/UNNAMED00025'
Recovery Slave PR00 previously exited with exception 1111
Errors in file /u01/app/oracle/diag/rdbms/xxxxxxx/xxxxxxx/trace/xxxxxxx_mrp0_22432.trc:
ORA-01111: name for data file 25 is unknown - rename to correct file
ORA-01110: data file 25: '/u01/app/oracle/product/11.2.0/db_1/dbs/UNNAMED00025'
ORA-01157: cannot identify/lock data file 25 - see DBWR trace file
ORA-01111: name for data file 25 is unknown - rename to correct file
ORA-01110: data file 25: '/u01/app/oracle/product/11.2.0/db_1/dbs/UNNAMED00025'
MRP0: Background Media Recovery process shutdown (xxxxxxx)

In the database - 

SQL> select name from v$datafile;
NAME
--------------------------------------------------------------------------------
+DATA/p2psfdom/datafile/domstab3.264.804084437
+DATA/p2psfdom/datafile/hadoopuser_tab.272.804085249
/u01/app/oracle/product/11.2.0/db_1/dbs/UNNAMED00025

The database is using ASM hence it should add DBF to ASM and not on disk. This behavior was controlled by DG parameter STANDBY_FILE_MANAGEMENT. 
This parameter was set to MANUAL in this env, hence the file was not propagated to ASM, hence needs a fix.

Following is the fix that one can use to overcome this sort of issue

-- Set the STANDBY_FILE_MANAGEMENT initialization to MANUAL on the standby database if its --- not 
SQL>   alter system set standby_file_management='manual';

-- Next rename the datafile: 

SQL > alter database create datafile ‘/u01/app/oracle/product/11.2.0/db_1/dbs/UNNAMED00025’ as '+DG_DATA’ size 8192m;

-- Next we re-enable auto standby file management.
SQL> alter system set standby_file_management='auto';

-- The last step on the standby database side
SQL> recover managed standby database disconnect from session;

Managed recovery should now be able to proceed normally.