open failure

Total System Global Area 621892184 bytes
Fixed Size 455256 bytes
Variable Size 553648128 bytes
Database Buffers 67108864 bytes
Redo Buffers 679936 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 2 - see DBWR trace file
ORA-01110: data file2: '/export/home/oracle/oradata/ems/undotbs01.dbf'


解决方法：
alter database datafile '/export/home/oracle/oradata/ems/undotbs01.dbf'offline drop;