Autotrace Output
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Thread: Autotrace Output

  1. #1
    Join Date
    Jan 2001
    Posts
    515

    Autotrace Output

    I have a large partitioned table and I did an autotrace on it and I am having a hard time figuring out a couple of things. Here it is:

    SQL>set autotrace traceonly
    SQL>select count(*) from abc.mytable where value_date >= '01mar03';

    Execution Plan
    ----------------------------------------------------------
    0 SELECT STATEMENT Optimizer=CHOOSE (Cost=3487 Card=1 Bytes=8)
    1 0 SORT (AGGREGATE)
    2 1 SORT* (AGGREGATE) :Q223400
    0

    3 2 PARTITION RANGE* (ITERATOR) :Q223400
    0

    4 3 TABLE ACCESS* (FULL) OF 'MYTABLE' (Cost=3487 C :Q223400
    ard=45581 Bytes=364648) 0



    2 PARALLEL_TO_SERIAL SELECT /*+ PIV_SSF */ SYS_OP_MSR(COUNT(*)) F
    ROM (SELECT /*+ NO_EXPAND ROWID(A2)

    3 PARALLEL_COMBINED_WITH_PARENT
    4 PARALLEL_COMBINED_WITH_PARENT


    What is the PARALLEL_COMBINED_WITH_PARENT and the (Cost=3487 Card=1 Bytes=8)?

    I have a Performance and Tuning book but the example they give is not like this. Is there a website or book that would better explain these outputs?

  2. #2
    Join Date
    Sep 2001
    Location
    NJ, USA
    Posts
    1,287
    How many CPUs and disk controllers on ur box?
    PARALLEL_COMBINED_WITH_PARENT -- this is parallel read operatior from the table
    and ur have "parent" and set of "childs" parallel read processes
    (perhaps from different partitions)

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