Java and JavaScript in the Database

Question about operating system calls from apex.

I created a java file which is wrapped with pl/sql like

create or replace java source named "ExternalCall" as
import java.io.*;
...
...

I do the steps from this web page http://www.oracle.com/global/de/community/tipps/oscalls/index.html
The page is in german, but for experienced users the code on this page says everything.

In apex i have an application which calls this function with the "move" command in a sql-report region.
Let's say move c:\work1\file.txt c:\work2\file.txt
Everything works fine on one host(pc) but if i want to transfer the file from my host to another one then
i get the messgage "no access" although i have read, write access on the other host.
By the way, on both hosts i have admin rights.

Why can't i transfer the file over a network ?

Thanks in advance for any kind of help.

Regards
Stefan