drop tablespace (missing datafile)

HI,

        how I could drop a tablespace of which I have missed the datafile ?

	The problem arise because I couldn't mount correctly my db instance
	because I've missed the datafile.

	I hope someone could help me.

	pietro
	
	---------------------
	the SVRMGR say:

	SVRMGR> connect internal
	Connected.
	SVRMGR> startup
	ORACLE instance started.
	Total System Global Area                          4754704 bytes
	Fixed Size                                          48400 bytes
	Variable Size                                     4222976 bytes
	Database Buffers                                   409600 bytes
	Redo Buffers                                        73728 bytes
	Database mounted.
	ORA-01157: cannot identify data file 6 - file not found
	ORA-01110: data file 6: '/tmp/prova.dbs'
	SVRMGR> connect system
	Password: 
	ORA-01033: ORACLE initialization or shutdown in progress
	SVRMGR>  drop tablespace prova;
	 drop tablespace prova
	 *
	 ORA-01109: database not open
	 
	--------------------