Why does SET ROLE start a transaction?

Question

Hi,
I wonder why SQL command SET ROLE starts a transaction?
Is it considered to be a DML command?
If yes, then why?
Check this simple PL/SQL example (where FND_ADMIN is any role granted to the user executing the code):
SET SERVEROUT ON
BEGIN
dbms_output.put_line('[1]');
dbms_output.put_line(dbms_transaction.local_transaction_id);
dbms_output.put_line('[2]');
dbms_session.set_role('FND_ADMIN');
dbms_output.put_line('[3]');
dbms_output.put_line(dbms_transaction.local_transaction_id);
dbms_output.put_line('[4]');
END;
It gives the following output:
[1]
[2]
[3]
6.40.1217
[4]
Regards
Håkan

Answer 1

Hm... as documentation states, DBMS_SESSION.SET_ROLE is, quote, "... equivalent to the SET ROLE SQL statement", unquote.
However, seems that it's doing something more than just SET ROLE:
SQL> commit;
Commit complete.
SQL> select sid, taddr
  2    from v$session
  3   where sid = (select sid from v$mystat where rownum = 1);
       SID TADDR
        46
SQL> set role CTXAPP;
Role set.
SQL> select sid, taddr
  2    from v$session
  3   where sid = (select sid from v$mystat where rownum = 1);
       SID TADDR
        46TADDR is empty – we don't have transaction and there is no transaction state object for our session.
However:
SQL> exec dbms_session.set_role('CTXAPP')
PL/SQL procedure successfully completed.
SQL> select sid, taddr
  2    from v$session
  3   where sid = (select sid from v$mystat where rownum = 1);
       SID TADDR
        46 5756BD74Why so? I don't know :) But obviously, DBMS_SESSION.SET_ROLE is not a precise equivalent to SET ROLE.
Regards.