Translation of ORACLE hints to DB2 hints

Question

Hi,
how can I translate the ORACLE hints to equivalent DB2 hints in the following SELECT statement:
====================================================================
    SELECT qmihqmnum qmihwarpl qmihwapos afihaufnr
      FROM qmih AS qmih
      INNER JOIN objk AS objk
        ON objkihnum = qmihqmnum
      INNER JOIN afih AS afih
        ON afihobknr = objkobknr
      INNER JOIN afko AS afko
        ON afkoaufnr = afihaufnr
      INNER JOIN afvc AS afvc
        ON afvcaufpl = afkoaufpl
        AND afvcaplzl = objkobzae
      INTO CORRESPONDING FIELDS OF TABLE lt_iwar
      WHERE afih~iphas = '2'
        AND afvc~phflg <> 'X'
        AND afko~gstrp <= lf_datum_eckstart
        AND qmih~warpl IN lr_warpln
        AND qmih~wapos IN lr_wapos
    %_HINTS
    ORACLE 'LEADING(T_00)'
    ORACLE 'USE_NL(T_00 T_01 T_02 T_03 T_04)'
    ORACLE 'INDEX(T_00 "QMIH~Z02")'
    ORACLE 'INDEX(T_01 "OBJK~M")'
    ORACLE 'INDEX(T_02 "AFIH~O")'
    ORACLE 'INDEX(T_03 "AFKO~0")'
    ORACLE 'INDEX(T_04 "AFVC~0")'.
====================================================================
Thanks a lot
Alex

Answer 1

Hello Hermann,
first of all thanks a lot for the quick reply.
In my example I'm referring to DB6.
I tested this statement without any hints resulting in a 4-5 times longer response time compared to the Oracle based system.
My biggest problem is, that the system uses index "C" to access table AFIH instead of using index "O" to join via field obknr.
Index "C" on table AFIH is defined as
-) MANDT
-) IPHAS
-) EQUNR
Index "O" is defined as
-) OBKNR
-) MANDT
Here's the EXPLAIN from ST05:
==========================================================================
   0 SELECT STATEMENT ( Estimated Costs =  1,962E+05 [timerons] ) num_rows tot_cost i/o_cost
          1 RETURN  6.3457E-02  1.9623E05  2.6207E04
              2 NLJOIN  6.3457E-02  1.9623E05  2.6207E04
                  3 [O] NLJOIN  3.9594E01  1.9563E05  2.6128E+04
                      4 [O] HSJOIN  1.5837E03  1.5969E05  2.1377E+04
                          5 [O] FETCH AFIH  4.8355E05  2.6256E04  3.4579E+03
                              6 IXSCAN AFIH~C #key columns:  2  4.8355E05  5.3460E02  8.3984E+01
                          7 <i> NLJOIN  5.9836E03  1.3342E05  1.7919E+04
                              8 [O] FETCH QMIH  5.7811E03  2.2441E03  5.7555E+02
                                  9 RIDSCN  5.7811E03  7.2107E01  8.0000E+00
                                     10 SORT  1.4452E03  1.8027E01  2.0000E+00
                                         11 IXSCAN QMIH~Z02 #key columns:  2  1.4452E03  1.7650E01  2.0000E+00
                                     12 SORT  1.4452E03  1.8027E01  2.0000E+00
                                         13 IXSCAN QMIH~Z02 #key columns:  2  1.4452E03  1.7650E01  2.0000E+00
                                     14 SORT  1.4452E03  1.8027E01  2.0000E+00
                                         15 IXSCAN QMIH~Z02 #key columns:  2  1.4452E03  1.7650E01  2.0000E+00
                                     16 SORT  1.4452E03  1.8027E01  2.0000E+00
                                         17 IXSCAN QMIH~Z02 #key columns:  2  1.4452E03  1.7650E01  2.0000E+00
                             18 <i> FETCH OBJK  1.0350E00  2.2700E01  3.0000E+00
                                 19 IXSCAN OBJK~M #key columns:  2  1.0350E00  1.5137E01  2.0000E+00
                     20 <i> FETCH AFKO  2.5000E-02  2.2700E01  3.0000E00
                         21 IXSCAN AFKO~0 #key columns:  2  1.0000E00  1.5136E01  2.0000E+00
                 22 <i> FETCH AFVC  1.6026E-03  1.5163E01  2.0032E00
                     23 IXSCAN AFVC~0 #key columns:  2  3.2053E-03  1.5139E01  2.0000E00
==========================================================================
So my question would be how to make the system use index "O" on table AFIH instead of using index "C".
Of course I studied note 868888. But still I don't know how to formulate hints for joins over more than two tables.
Maybe you can give me a how to do that.
Thanks a lot
Alex