Using oradebug one can get a dump of sessions parameters that are modified at session level, like optimization parameters.
SQL> alter session set sql_trace=true;
Session altered.
SQL> alter session set optimizer_mode=first_rows;
Session altered.
-- connect to session
SQL> oradebug setmypid
Statement processed.
SQL> oradebug dump modified_parameters 1;
Statement processed.
SQL> oradebug tracefile_name;
i:\db\oracle\testdb\diagnostic_dest\diag\rdbms\testdb_a\testdb\trace\testdb_ora_4908.trc
Contents of the tracefile:
…
*** 2012-05-28 14:35:25.005
Processing Oradebug command ‘dump modified_parameters 1’
DYNAMICALLY MODIFIED PARAMETERS:
sql_trace = TRUE
optimizer_mode = FIRST_ROWS
*** 2012-05-28 14:35:25.005
Oradebug command ‘dump modified_parameters 1’ console output: