We occurs this error mostly in case of incomplete recovery.....
SQL> startup force
ORACLE instance started.
Total System Global Area 801701888 bytes
Fixed Size 2232640 bytes
Variable Size 331353792 bytes
Database Buffers 461373440 bytes
Redo Buffers 6742016 bytes
Database mounted.
ORA-01589: must use RESETLOGS or NORESETLOGS option for database open
SQL> recover database until cancel using backup controlfile;
ORA-00283: recovery session canceled due to errors
ORA-01110: data file 5: '/u01/oracle/11.2/sachin/sys/sachin.dbf'
ORA-01157: cannot identify/lock data file 5 - see DBWR trace file
ORA-01110: data file 5: '/u01/oracle/11.2/sachin/sys/sachin.dbf'
SQL> alter database datafile 5 offline;
SQL> alter database open resetlogs;