Actually this has been resolved.

It is OS directory permission issue. Directly login used group permission while "oracle" is the part of the group. The sqlnet login might need the owner permission I think? After asking the system change the file permission: to have the directory owned by "oracle", then it worked.

Just in case that other people come cross the simailar issue.

Best wishes,

Zhuang

====================================================
Hi Tom,

Hope you can answer this:

The following SQL
</>

DECLARE

v_file_contents CLOB := 'test';
v_filename VARCHAR2(100) := 'test.txt';
v_filepath VARCHAR2(1000) := 'ELEMENTSFEED';

BEGIN

dbms_xslprocessor.clob2file(
cl => v_file_contents,
flocation => v_filepath,
fname => v_filename,
csid => nls_charset_id('UTF8')
);

END;
</>

If I login to the database directly by "sqlplus username/password", it runs successfully.
but if run as "sqlplus username/password@tnsname", it gives the following error:
ERROR at line 1:
ORA-29283: invalid file operation
ORA-06512: at "SYS.UTL_FILE", line 536
ORA-29283: invalid file operation
ORA-06512: at "XDB.DBMS_XSLPROCESSOR", line 121
ORA-06512: at line 9

Why @tnsnames make such big difference? It only happened on one database.

Thanks,

Zhuang