PAralel query tunnig

Question

Good day everybody, im working with oracle 9.2.0.8 on AIX 5L
I recently mounted the filesystems of the datafiles and indexes (not the product) in DIRECT IO mode (mount -o dio /path_of_files)
but it happens that some parallel query executions doesnt get any benefit from the change... actually they had been downgrades... consider the following Tkproff extract, versus the original timing....
The point is that direct io actually improves several queries, but those related to paralell execution are suffering this downgrade, i think, related to this PX Deq: Execute Reply
here are some related parameters and below the tkprof extracts ...
filesystemio_options     SETALL
parallel_adaptive_multi_user     TRUE
parallel_automatic_tuning     TRUE
parallel_execution_message_size          8192
parallel_max_servers          160
parallel_server_instances     1
parallel_threads_per_cpu     2
DIRECT IO
Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
db file sequential read 105442 2.09 1490.70
  process startup                                17        0.02          0.43
  PX Deq: Join ACK                                2        0.01          0.01
  PX Deq: Parse Reply                             6        0.22          0.42
PX Deq: Execute Reply 507 1.95 797.61
  PX Deq Credit: need buffer                     58        0.51          2.40
  PX Deq Credit: send blkd                       50        1.09          5.16
  PX Deq: Table Q Normal                        337        0.55          1.96
  log file switch completion                      4        0.02          0.04
  log buffer space                               51        0.97          6.32
  log file sync                                   9        0.08          0.23
  PX Deq: Signal ACK                              5        0.04          0.06
  enqueue                                         5        0.00          0.00
  SQL*Net message to client                       1        0.00          0.00
  SQL*Net message from client                     1        0.07          0.07
ORIGINAL ONE
Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  process startup                                12        0.03          0.31
  PX Deq: Join ACK                                8        0.00          0.00
  PX Deq: Parse Reply                            12        0.16          0.19
PX Deq: Execute Reply 137 1.95 119.74
db file sequential read 104347 0.39 555.89
  PX Deq Credit: need buffer                      2        0.00          0.00
  log buffer space                               98        0.42          8.15
  log file switch completion                      4        0.38          0.49
  log file sync                                  27        0.62          2.61
  PX Deq: Table Q Normal                         23        0.00          0.00
  PX Deq: Signal ACK                              6        0.00          0.00
  enqueue                                         1        0.00          0.00
  SQL*Net message to client                       1        0.00          0.00
  SQL*Net message from client                     1        0.06          0.06Thanks in advance.

Answer 1

First of all, thanks for your help...
and actually, there was one table that lacked parallel flag... i fixed it but...
yet, the PX Deq: Execute Reply is the top wait event... in the master tkprof..
and i think that your guesswork was accurate, take a look...
Operation                    Object Name     Rows     Bytes     Cost     Object Node     In/Out     PStart     PStop
INSERT STATEMENT          Optimizer Mode=CHOOSE          3             5866                                          
  NESTED LOOPS                                   3       672       5866       P->S       QC (RANDOM)      
    HASH JOIN                                   3       444       5865       PCWP                        
      TABLE ACCESS BY INDEX ROWID     PRD982E.IMP_CONCEPTO     1       33       1       PCWC                        
        NESTED LOOPS                              15 K     1 M     5859       P->P       HASH             
          HASH JOIN                              74 K     4 M     2132       PCWP                        
            TABLE ACCESS BY INDEX ROWID     PRD982E.BDG_MOVIMIENTOS     74 K     3 M     1240       S->P       HASH             
              INDEX RANGE SCAN          PRD982E.SAP_BDG_IDX01     148 K           548                                          
            TABLE ACCESS FULL          PRD982E.SUMCON          1 M     13 M     892       P->P       HASH             
          INDEX RANGE SCAN          PRD982E.PK_IMP_CONCEPTO     1             1       PCWP                        
      TABLE ACCESS FULL               RELACIONES_ASIENTOS     40 K     1 M     6       P->P       HASH             
    TABLE ACCESS BY INDEX ROWID          PRD982E.RECIBOS          1       76       1       PCWP                        
      INDEX UNIQUE SCAN               PRD982E.PK_RECIBOS     1                   PCWP                        
call     count       cpu    elapsed       disk      query    current        rows
Parse        1      0.02       1.48          0          0          0           0
Execute      1     21.26     615.80      18451      28609     530507      399299
Fetch        0      0.00       0.00          0          0          0           0
total        2     21.28     617.29      18451      28609     530507      399299
Misses in library cache during parse: 1
Optimizer goal: CHOOSE
Parsing user id: 934
Rows     Row Source Operation
      0  NESTED LOOPS
      0   HASH JOIN
      0    TABLE ACCESS BY INDEX ROWID IMP_CONCEPTO
      0     NESTED LOOPS
      0      HASH JOIN
      0       TABLE ACCESS BY INDEX ROWID BDG_MOVIMIENTOS
152295        INDEX RANGE SCAN SAP_BDG_IDX01 (object id 34358)
      0       TABLE ACCESS FULL SUMCON
      0      INDEX RANGE SCAN PK_IMP_CONCEPTO (object id 26842)
      0    TABLE ACCESS FULL SAP_RELACIONES_ASIENTOS_MV
      0   TABLE ACCESS BY INDEX ROWID RECIBOS
      0    INDEX UNIQUE SCAN PK_RECIBOS (object id 28131)
Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  process startup                                18        0.97          1.42
  PX Deq: Join ACK                                2        0.21          0.21
  PX Deq: Parse Reply                             7        0.07          0.15
  PX Deq: Execute Reply                         570        1.95        498.31
  db file sequential read                     18450        0.20         74.02
  log file switch completion                      3        0.19          0.23
  PX Deq: Table Q Normal                         31        0.08          0.13
  PX Deq: Signal ACK                              9        0.02          0.03
  enqueue                                         2        0.00          0.00
  log file sync                                   1        0.01          0.01
  SQL*Net message to client                       1        0.00          0.00
  SQL*Net message from client                     1        0.20          0.20
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