How to take some session parameters into your variables

There are a few of posibilities. One of them: sys_context().
As you can read at 
http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions165.htm 
it is a great deal of information within...
Just try this command:

select sys_context('USERENV','SESSION_USER') as username,   sys_context('USERENV','IP_ADDRESS') as ipaddress,   sys_context('USERENV','HOST') as machinename, sys_context('USERENV','module') module, sys_context('USERENV','action') action,
sys_context('USERENV','client_identifier') client_id, sys_context('USERENV','client_info') client_info, sys_context('USERENV','current_schema') schema, sys_context('USERENV','current_schemaid') schemaid,sys_context('USERENV','current_sql') sql from dual;

and maybe you'll notice a lot of parameters that you would wanted them in some audit tables or used by some triggers. For instance, i used the <module> value in order to block a Forms application to change the value of a column in a table.
Enjoy!