select MACHINE,
       PROGRAM,
       OSUSER,
       USERNAME
 from V$SESSION 
where sid=(select sys_context('USERENV','SID') from dual);

To get more information of the current session use this: DESC V$SESSION.

Note: Your user need a  GRANT SELECT ON V_$SESSION TO username;

How to get MACHINE name, PROGRAM name, operative system USER and the USERNAME related to the current Oracle Database Session

SQL