SELECT host_name FROM v$instance;

SELECT machine FROM v$session WHERE audsid = USERENV('SESSIONID');

set linesize 120
set feedback off
set serveroutput on
DECLARE
  my_name   varchar2(15);
  my_ip     varchar2(15);
  my_server varchar2(15);
  v_host_name varchar2(15);
  v_ip_address varchar2(15);
BEGIN
  DBMS_OUTPUT.PUT_LINE('MY NAME         MY IP ADDRESS   SERVER NAME     SERVER_IP       SERVER');
  DBMS_OUTPUT.PUT_LINE('--------------- --------------- --------------- --------------- ---------------');
  SELECT UTL_INADDR.GET_HOST_NAME(v_host_name) into v_host_name FROM DUAL;
  SELECT UTL_INADDR.GET_HOST_ADDRESS(v_host_name) into v_ip_address FROM DUAL;
  SELECT RPAD(sys_context('USERENV','SESSION_USER'),15,' ') MY_NAME,
         RPAD(sys_context('USERENV','IP_ADDRESS'),15,' ') MY_IP ,
         RPAD(SYS_CONTEXT('USERENV', 'DB_NAME'),15,' ') SERVER
    INTO my_name, my_ip, my_server
    FROM DUAL;
  DBMS_OUTPUT.PUT_LINE(rpad(my_name,15,' ')||' '||
                       rpad(my_ip,15,' ')||' '||
                       rpad(my_server,15,' ')||' '||
                       rpad(v_ip_address,15,' ')||' '||
                       rpad(v_host_name,15,' '));
END;
.
/
select
.
set feedback on