Query session parameter values of running session
I know this question is more than a year old, but in case anyone stumbles here like I did, you can query V$SES_OPTIMIZER_ENV:

SYS&gt; select name, value 
        from  V$SES_OPTIMIZER_ENV 
        where sid=54 
           and name='hash_area_size';

NAME                                     VALUE
—————————————- ————————-
hash_area_size                           100000


Source: http://oracleinaction.com/other-session-params/