SQL> select  sys_context('userenv', 'os_user') from dual;

SYS_CONTEXT('USERENV','OS_USER')
------------------------------------
klrice

 <<< a short command to set java properties >>>
 <<< which is the same as a -D property     >>>

SQL> set property user.name kris
Setting user.name to kris (klrice)


SQL> @connect-klrice
Connected.
SQL> select  sys_context('userenv', 'os_user') from dual;

SYS_CONTEXT('USERENV','OS_USER')
----------------------------------
kris

SQL>