SQL>  select /*+ NO_INDEX(T_IDX) */ * from t where empno=7369;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM
---------- ---------- --------- ---------- --------- ---------- ----------
    DEPTNO
----------
      7369 SMITH      CLERK           7902 17-DEC-80        800
        20

Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=2 Card=1 Bytes=32)
   1    0   TABLE ACCESS (BY INDEX ROWID) OF 'T' (Cost=2 Card=1 Bytes=
          32)

   2    1     INDEX (RANGE SCAN) OF 'T_IDX' (NON-UNIQUE) (Cost=1 Card=
          1)

-- Now specify the table and index in the NO_INDEX hint

SQL> select /*+ NO_INDEX(T T_IDX) */ * from t where empno=7369;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM
---------- ---------- --------- ---------- --------- ---------- ----------
    DEPTNO
----------
      7369 SMITH      CLERK           7902 17-DEC-80        800
        20

Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=2 Card=1 Bytes=32)
   1    0   TABLE ACCESS (FULL) OF 'T' (Cost=2 Card=1 Bytes=32)

-- or just the table_name to disallow all indexes 

SQL> select /*+ NO_INDEX(T) */ * from t where empno=7369;

     EMPNO ENAME      JOB              MGR HIREDATE         SAL       COMM
---------- ---------- --------- ---------- --------- ---------- ----------
    DEPTNO
----------
      7369 SMITH      CLERK           7902 17-DEC-80        800
        20

Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=2 Card=1 Bytes=32)
   1    0   TABLE ACCESS (FULL) OF 'T' (Cost=2 Card=1 Bytes=32)

SQL> drop table t;

Table dropped.

SQL> create table t as select * from scott.emp;

Table created.

SQL> show parameter optimizer_mode

NAME                                 TYPE
------------------------------------ --------------------------------
VALUE
------------------------------
optimizer_mode                       string
CHOOSE

-- There are no statistics on this table

SQL> select num_rows,blocks from user_tables where table_name='T';

  NUM_ROWS     BLOCKS
---------- ----------

SQL> set autotrace traceonly explain
SQL> select /*+ FULL(T) */ * from t;

Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT Optimizer=CHOOSE (Cost=2 Card=327 Bytes=284
          49)

   1    0   TABLE ACCESS (FULL) OF 'T' (Cost=2 Card=327 Bytes=28449)

-- as seen above, CBO is still used even when there are no statistics on the table,becos of the hint.

-- Now lets go one step further and set the optimizer_goal to RULE

SQL> alter session set optimizer_goal=rule;

Session altered.

SQL> select /*+ FULL(T) */ * from t;

Execution Plan
----------------------------------------------------------
   0      SELECT STATEMENT Optimizer=RULE (Cost=2 Card=2000 Bytes=1740
          00)

   1    0   TABLE ACCESS (FULL) OF 'T' (Cost=2 Card=2000 Bytes=174000)

-- although it says Optimizer=RULE , we know that CBO is still forced as we see the Cost,Card etc.