ORA-01111: name for data file is unknown - rename to correct file

If your MRP process not Applying logs and if you see this error in alert log;

ORA-01111: name for data file 80 is unknown - rename to correct file
ORA-01110: data file 80: '/u01/app/oracle/product/19.0.0/dbhome_1/dbs/UNNAMED00080'
ORA-01157: cannot identify/lock data file 80 - see DBWR trace file
ORA-01111: name for data file 80 is unknown - rename to correct file
ORA-01110: data file 80: '/u01/app/oracle/product/19.0.0/dbhome_1/dbs/UNNAMED00080'
2022-12-03T01:09:09.393727+03:00
Background Media Recovery process shutdown

This mean is you have to rename and locate 80. datafile on standby database.

ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;
ALTER SYSTEM SET STANDBY_FILE_MANAGEMENT=MANUAL scope=both;
select FILE# from v$recover_file where error like '%FILE%';
     FILE#
----------
         80

Find name of datafile from Primary Database

select NAME from v$datafile where file#=80;

if not asm ;

ALTER DATABASE CREATE DATAFILE '/u01/app/oracle/product/19.0.0/dbhome_1/dbs/UNNAMED00080' as '/u01/app/oracle/product/19.0.0/dbhome_1/dbs/ts_index.3635.1122300859';
ALTER SYSTEM SET STANDBY_FILE_MANAGEMENT=AUTO;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT;

if asm ;

alter database create datafile 80 as NEW;
ALTER SYSTEM SET STANDBY_FILE_MANAGEMENT=AUTO;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT;