ORA-01111: Name For Data File Is Unknown

[big]

Hi,
I have this error:
select count(*) from AUDSYS.UNIFIED_AUDIT_TRAIL
                            *
ERROR at line 1:
ORA-00376: file 8 cannot be read at this time
ORA-01111: name for data file 8 is unknown - rename to correct file
ORA-01110: data file 8: $ORACLE_HOME/dbs/MISSING00008

ls $ORACLE_HOME/dbs/MISSING00008

$ORACLE_HOME/dbs/MISSING00008 not found

Also I queried database:
select * from v$recover_file where error like '%FILE%';

     FILE# ONLINE  ONLINE_ ERROR         CHANGE# TIME          CON_ID
---------- ------- ------- ---------- ---------- --------- ----------
         8 OFFLINE OFFLINE FILE                0                    0
                           MISSING

SQL> select name from v$datafile where name like '%UNNAMED%';

no rows selected

What is the solution? We are not in RAC. Usually the proposed soultions are for RAC.

Thanks.

[ErmanArslansOracleBlog]

There is a missing datafile there.

When a datafile goes missing at the operating system level, you should need to restore and recover it from a backup.

RMAN>restore datafile <missing file id>;
RMAN>recover datafile <missing file id>;
RMAN>sql 'alter database datafile <missing file id> online';

There are other possible causes as well;

Such as;
Incorrect access permissions
Offline tablespace
Physical corruptions
Logical corruptions
Inconsistencies ( control file is older or newer than the data files and online redo logs)
I/O failures (limit on the number of open files exceeded, channels inaccessible, network or I/O error)

So keep those in mind and check the following MOS notes;

11g Data Recovery Advisor: How to recover from missing datafile (Doc ID 465946.1)
Recreating a missing datafile with no backups (Doc ID 1149946.1)