由于误删了表空间，导致在数据库启动时报错

SQL> startup
ORACLE instance started.

Total System Global Area 1.3429E+10 bytes
Fixed Size 2239192 bytes
Variable Size 9999222056 bytes
Database Buffers 3221225472 bytes
Redo Buffers 205967360 bytes
Database mounted.
ORA-01157: cannot identify/lock data file 11 - see DBWR trace file
ORA-01110: data file 11: '/oracle/oradata/orcl/itreasury.dbf'

解决办法：

依次执行下面的命令

shutdown immediate;

startup mount;

alter database datafile 11 offline drop;

11 表示上面报错的文件编号。

recover database;

alter database open;

shutdown immediate;

startup;

此时就可以正常启动了。