Why my table is not being audited?

Question

hi all, please help ! thanks! i don't understand. why there is no record in dba_audit_trail table for my 'insert' statement?
SQL> show parameter audit_trail
NAME TYPE VALUE
audit_trail string DB
SQL>
SQL>audit all;
Audit succeeded.
SQL> audit all privileges;
Audit succeeded.
SQL> select audit_option from dba_stmt_audit_opts where audit_option like '%INSERT%';
AUDIT_OPTION
INSERT ANY TABLE
SQL>
SQL> show user
USER is "IRXXL99"
SQL> insert into test_audit (id, name) values ('3', 'hello');
1 row created.
SQL> commit;
Commit complete.
SQL> show user
USER is "SYS"
SQL> select obj_name, action_name from dba_audit_trail where obj_name = 'TEST_AUDIT';
no rows selected
SQL>

Answer 1

yeah.. it doesn't make any sense. something must be done wrong or missing !
SQL> insert into test_audit (id, name) values ('3', 'hello');
1 row created.
SQL> commit;
Commit complete.
SQL>
SQL> select user_name, audit_option from dba_stmt_audit_opts where audit_option like '%INSERT%';
USER_NAME AUDIT_OPTION
INSERT ANY TABLE
SQL> select obj_name , action_name from dba_audit_trail where obj_name = 'TEST_AUDIT';
no rows selected
SQL>