SQL & PL/SQL

Hi Guys,

I have created after login trigger to audit user connections , im relying on SYS_CONTEXT for some of the variables

v_user_name:=SYS_CONTEXT('USERENV','SESSION_USER');
v_from_host:=SYS_CONTEXT('USERENV','HOST') ;
v_ip:=SYS_CONTEXT('USERENV','IP_ADDRESS') ;
v_osuser:=SYS_CONTEXT('USERENV','OS_USER') ;

select program into v_program from v$session where audsid=sys_context('USERENV','SESSIONID');

but have realized that some time SYS_CONTEXT('USERENV','IP_ADDRESS') ; returns null ! does anyone know why ? or is there any better place to look for IP address ?

Im not sure about SYS_CONTEXT('USERENV','HOST') ; ( assuming it always returns someting ...

thanks for reading.
Ali