Oracle backup fails with "could not read file header for datafile 5 error reason 1" error

When attempting to perform a database backup I recived the following error:

"could not read file header for datafile 5 error reason 1"

To diagnoze the error, first check the DBA_DATA_FILES view, the file with file_id=5:

SELECT FILE_ID, FILE_NAME FROM DBA_DATA_FILES;

The results returned will look something like that:

 FILE_ID                   FILE_NAME
-------------------------------------------------------------------
1                /u01/oradata/DBName/system01.dbf

2                /u01/oradata/DBName/sysaux01.dbf

3                /u01/oradata/DBName/undotbs01.dbf

4                /u01/oradata/DBName/users01.dbf

5                /u01/app/oracle/product/11.2.0.3/dbs/MISSING00005 

Solution: Check your data files to see which one is missing, then rename the missing file:

ALTER DATABASE RENAME FILE '/u01/app/oracle/product/11.2.0.3/dbs/MISSING00005' TO '/u01/app/oracle/oradata/DBName/mydatefile1.dbf';

followed by

RECOVER DATAFILE 5;