I intended to drop a tablespace which is not usable any more. But I removed the datafile of that tablespace by mistake before running DROP TABLESPACE statement. So I got the following error when I tried to drop the tablespace now.

SQL> drop tablespace XXXXX including contents;
drop tablespace XXXXX including contents
ERROR at line 1:
ORA-01115: IO error reading block from file 20 (block # 1)
ORA-01110: data file 20: '/usr/local/oracle/oradata/db1/XXXXX.dbf'
ORA-27091: skgfqio: unable to queue I/O
ORA-27072: skgfdisp: I/O error
SVR4 Error: 25: Inappropriate ioctl for device
Additional information: 1

Could any body tell me how to drop this tablespace ?

Thanks very much.