LIO/PIO and redo size

Question

Hi,
I have the query below:
with D_FLO_PTN as (SELECT   *
            FROM   FLO_PTN
           WHERE   FLO_PTN.ID_ETU IN (SELECT   id_etu
                                        FROM   music_adm.adm_users_rights
                                       WHERE   user_name = UPPER ('SALG_CB'))
                   OR FLO_PTN.PDTETU IN
                           (SELECT   id_pdtetu
                              FROM   music_adm.adm_users_rights
                             WHERE   user_name = UPPER ('SALG_CB'))
                   OR EXISTS
                        (SELECT   1
                           FROM   music_adm.adm_users_rights
                          WHERE       id_etu = 0
                                  AND id_pdtetu = '0'
                                  AND user_name = UPPER ('SALG_CB'))),
D_FAI_VIS as (SELECT   *
            FROM   FAI_VIS
           WHERE   FAI_VIS.ID_ETU IN (SELECT   id_etu
                                        FROM   music_adm.adm_users_rights
                                       WHERE   user_name = UPPER ('SALG_CB'))
                   OR FAI_VIS.PDTETU IN
                           (SELECT   id_pdtetu
                              FROM   music_adm.adm_users_rights
                             WHERE   user_name = UPPER ('SALG_CB'))
                   OR EXISTS
                        (SELECT   1
                           FROM   music_adm.adm_users_rights
                          WHERE       id_etu = 0
                                  AND id_pdtetu = '0'
                                  AND user_name = UPPER ('SALG_CB'))),
d_dim_etu as (SELECT   *
            FROM   DIM_ETU
           WHERE   DIM_ETU.ID_ETU IN (SELECT   id_etu
                                        FROM   music_adm.adm_users_rights
                                       WHERE   user_name = UPPER ('SALG_CB'))
                   OR DIM_ETU.PDTETU IN
                           (SELECT   id_pdtetu
                              FROM   music_adm.adm_users_rights
                             WHERE   user_name = UPPER ('SALG_CB'))
                   OR EXISTS
                        (SELECT   1
                           FROM   music_adm.adm_users_rights
                          WHERE       id_etu = 0
                                  AND id_pdtetu = '0'
                                  AND user_name = UPPER ('SALG_CB')))                                
SELECT   TRIM (TO_CHAR (D_FLO_PTN.PTNNUMETU, '00000')),
         FLO_ITM.FMLNOMPAP,
         FLO_ITM.ITMNOMPAP,
         FLO_ITM.ITMVALCHR,
         FLO_ITM.ITMVALNUM,
         D_FAI_VIS.VISCOD,
         TRIM (TO_CHAR (D_FLO_PTN.NBRCEN, '0000')),
         TRIM (TO_CHAR (D_FAI_VIS.ID_ETU, '000')) || '-'
         || TRIM(TO_CHAR (
                    SUBSTR (D_FAI_VIS.ID_PTN,
                            1,
                            LENGTH (D_FAI_VIS.ID_PTN) - 5),
                    '00000'
         || '-'
         || D_FAI_VIS.VISCOD,
         D_DIM_ETU.NUMETU,
         D_FLO_PTN.LIBPAY,
         FLO_ITM.ITMVALNUM,
         D_FAI_VIS.VISDATTXT,
         FLO_ITM.ITMVALNUM,
         FLO_ITM.FMLKEYVAL
  FROM  
         D_FLO_PTN,
         FLO_ITM,
         D_FAI_VIS,
         D_DIM_ETU
WHERE       (FLO_ITM.ID_VIS = D_FAI_VIS.ID_VIS)
         AND (D_FLO_PTN.ID_PTN = D_FAI_VIS.ID_PTN)
         AND (D_DIM_ETU.ID_ETU = D_FLO_PTN.ID_ETU)
         AND (    D_DIM_ETU.NUMETU IN ('CL2-38093-011')
              AND FLO_ITM.FMLNOMPAP IN ('MMS')
              AND (D_FLO_PTN.INDSLC = 'YES')
              AND TRIM (TO_CHAR (D_FLO_PTN.PTNNUMETU, '00000')) IN
                       (SELECT   TRIM (
                                    TO_CHAR (D_FLO_PTN.PTNNUMETU, '00000')
                          FROM    D_FLO_PTN,
                                 FLO_ITM,
                                 D_FAI_VIS
                         WHERE   (FLO_ITM.ID_VIS = D_FAI_VIS.ID_VIS)
                                 AND (D_FLO_PTN.ID_PTN = D_FAI_VIS.ID_PTN)
                                 AND (    FLO_ITM.ITMNOMPAP IN ('TMMS_D')
                                      AND FLO_ITM.ITMVALNUM <= 20
                                      AND D_FAI_VIS.VISCOD IN ('ASSE'))))2 things I don't understand
- almost LIO ~ PIO but I have 2.5GB for the buffer cache
- redo size, I know about delayed block cleanout
but the second execution should return redo size =0 no ?
I am the only user on the database
11.2.0.1
1st execution
       1879  recursive calls
        332  db block gets
     250090  consistent gets
     248221  physical reads
       1804  redo size
     631470  bytes sent via SQL*Net to client
      14706  bytes received via SQL*Net from client
       1090  SQL*Net roundtrips to/from client
          1  sorts (memory)
          0  sorts (disk)
      16329  rows processed
2nd execution
       1879  recursive calls
        332  db block gets
     250423  consistent gets
     248220  physical reads
       1732  redo size
    1149536  bytes sent via SQL*Net to client
      14706  bytes received via SQL*Net from client
       1090  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
      16329  rows processed

Answer 1

user12045475 wrote:
2 things I don't understand
- almost LIO ~ PIO but I have 2.5GB for the buffer cache
- redo size, I know about delayed block cleanout
but the second execution should return redo size =0 no ?
I am the only user on the database
11.2.0.1
2nd execution
1879  recursive calls
332  db block gets
250423  consistent gets
248220  physical reads
1732  redo size
1149536  bytes sent via SQL*Net to client
14706  bytes received via SQL*Net from client
1090  SQL*Net roundtrips to/from client
0  sorts (memory)
0  sorts (disk)
16329  rows processed
Given the amount of work you're doing, the actual redo generated is not worth worrying about other than for reasons of curiosity.
LIO ~ PIO often indicates table scans or index fast full scans - and on 11.2 such scans can use serial direct reads; this would be sufficient to answer both your questions:
a) On direct path reads the blocks are read into the PGA, not the buffer cache, so you have to re-read them on the second execution
b) On direct path read you can do cleanout and generate redo, but the blocks are not in the cache so they don't get written back to the database, so you repeat the cleanout. (A small variation in redo could indicate some cleanout taking place on space management blocks which, I think, will go through the cache).
Regards
Jonathan Lewis