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  1. #1
    Join Date
    Apr 2002
    Posts
    5

    Unanswered: update statistics

    hi,

    who can give a simple explanation of the difference between update statistics low/medium/high ?

    thanks

  2. #2
    Join Date
    May 2002
    Location
    Osnabrueck Germany
    Posts
    59
    Hi,
    i didn't know it either,
    but found an explanation:

    2-638 Informix Guide to SQL: Syntax
    UPDATE STATISTICS
    LOW The database server updates the statistical data in the
    systables, syscolumns, and sysindexes system catalog
    tables. This mode causes the least amount of information to
    be gathered. This mode executes more quickly than the
    HIGH and MEDIUM modes.
    HIGH In addition to performing the functions of the LOW mode,
    the database server updates the data distribution statistics
    in the sysdistrib system catalog table. The constructed
    distribution is exact. Because of the time required to gather
    this information, this mode executes more slowly than the
    LOW and MEDIUM modes.
    MEDIUM In addition to performing the functions of the LOW mode,
    the database server updates the data distribution statistics
    in the sysdistrib system catalog table. The database server
    obtains the data for the distributions by sampling rather
    than by scanning all the rows. This mode executes more
    quickly than the HIGH mode but more slowly than the
    LOW mode.
    Juergen Ladwig

  3. #3
    Join Date
    Nov 2001
    Location
    Germany
    Posts
    14
    Read the valuable article "Understanding and Tuning Update Statistics" at
    http://www7b.boulder.ibm.com/dmdd/zo...203miller.html

    I find it excellent...


    Murat

  4. #4
    Join Date
    Apr 2002
    Posts
    5
    thanks, Murat

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