I'll try to answer your questions:

1) whether the datafile here (step 4) refers to source or target database.

The file listed in the import command needs to be the filename on the TARGET database. This should be the file that you copied in step 3.


2) when i create the tablespace, the extension i get is "testing.ora" but not "testing.dbf". Is
that anything wrong or i just uses it ?

Yes, the datafile name will have .ora since that is the filename you gave it in step 3 and step 4. If you want to use .dbf, just use .dbf when you copy the file (step3) (and also in step 4)


3) the step 3 mention copy files to new location.
(is that correct if i just copy file to the
target database with the
path "c:\oracle\oradata\aaa\testing.ora" and
copy "export.dmp" to the same path.

I'm not sure I completely understand the question, but what you want to do is copy the datafile to the new location to be used by the target database. If the target database is on another machine, you will also need to copy the export.dmp. If the target is on the same machine, you can just keep the export.dmp where it is.


4) do i need to write down the ownership for
example FROMUSER, TOUSER?

No, since you are copying at a tablespace level.

For more information on how to do transportable tablespaces, please see the document on this site: http://www.dbasupport.com/oracle/ora8/page9.shtml

(There is one typo in this document though... you should copy the files before you make them READ-WRITE! )

Good Luck!
Jodie