Datafiles/tempfiles is use by process

@orcl

Oracle 11.2.0.4.0, Windows 7 Pro SP1

I have a little script to drop some users and delete their data- and tempfiles to have a fresh start after that

and can import a database newly.

drop.sql:

drop user someuser cascade;
drop user someotheruser cascade ;
alter tablespace someuser_data offline;
drop tablespace someuser_data including contents and datafiles cascade constraints;
drop tablespace someuser_temp;
quit;

And in the drop.bat I have:

sqlplus system/@orcl as sysdba @drop.sql

del c:\app\kuku\oradata\orcl\someuser_temp.dbf

The above leads to an error message, saying that the fiel to be deleted is being used by another process.