Error At run time:

SQL> conn / as sysdba

Connected.

SQL> select * from scott.emp;

select * from scott.emp

                    *

ERROR at line 1:

ORA-01116: error in opening database file 4

ORA-01110: data file 4: '/home/oracle/DB/INDIAN/users01.dbf'

ORA-27041: unable to open file

Intel SVR4 UNIX Error: 2: No such file or directory

Additional information: 3

Step 1: Check data file Status.

SQL> select * from v$backup;

     FILE# STATUS                CHANGE# TIME

---------- ------------------ ---------- ---------

         1 NOT ACTIVE                  0

         2 NOT ACTIVE                  0

         3 NOT ACTIVE                  0

         4 FILE NOT FOUND         0

         5 NOT ACTIVE                  0

Step 2: offline missing datafile

SQL> alter database datafile ‘ offline;

Step 3: Recover datafile;

SQL> recover datafile 4;