Results 1 to 5 of 5
  1. #1
    Join Date
    Oct 2007
    Posts
    61

    Unanswered: Statistic HIGH MEDIUM LOW

    Hello,

    I'd like to understand about Statistic...

    Well, my doubts are :
    1) I need run this sequence LOW MEDIUM AND HIGH statistic for the same table ??

    2) What the difference between LOW, MEDIUM AND HIGH ?

    3) IF i don't know the index from one table, and I run ex:

    UPDATE STATISTICS HIGH FOR TABLE consumo_teorico DISTRIBUTIONS ONLY;

    I got the same performance if I knew the index ???

  2. #2
    Join Date
    Apr 2007
    Location
    Jundiai / SP - Brasil
    Posts
    311

    Cool

    The manual (Performance Guide) say a lot things about guide lines to update statistics and have some articles on IBM site about this.
    But, the basic guide lines are:
    Medium and big tables:
    - update statistics HIGH in head columns (first columns) from any index
    - update statistics medium to another's columns where is part of a index
    - update statistics medium to columns where is used to filter.
    to small tables:
    - update statistics high , all columns

    Execute update statistics more frequently on tables where the data are modified frequently.
    Example:
    if you have a table with all move of a stock system , and all days have delete/inserts/updates on this table, consider executing the update statistics at least 1 time for week.


    Link to All PDFs manuals , all versions, free of charge:
    http://www-306.ibm.com/software/data...ubs/library/#3

    Creating Data Distributions
    http://publib.boulder.ibm.com/infoce...13query1-20817

    Updating Statistics on Very Large Databases
    http://publib.boulder.ibm.com/infoce...69%73%74%22%20

    Updating Statistics for Join Columns
    http://publib.boulder.ibm.com/infoce...69%73%74%22%20

    Somes TechNotes from IBM Support Site:
    http://www-1.ibm.com/support/search.....y=0&ibm-go=Go
    ________________________________________
    César Inacio Martins
    Jundiai / SP - Brasil
    http://www.imartins.com.br/informix - em Português
    http://www.imartins.com.br/informix - English (translated by Google).
    ________________________________________

  3. #3
    Join Date
    Apr 2007
    Location
    Jundiai / SP - Brasil
    Posts
    311
    I forgot..

    include on basic guide lines:
    First : - update statistics LOW to all tables.
    ________________________________________
    César Inacio Martins
    Jundiai / SP - Brasil
    http://www.imartins.com.br/informix - em Português
    http://www.imartins.com.br/informix - English (translated by Google).
    ________________________________________

  4. #4
    Join Date
    Oct 2007
    Posts
    61
    I was thinking about u said..


    Well, My big table has around 4 Million lines and Small tables 120 thousands lines..


    My database isn`t 24 / 7, so I can put in crontab to run tonight...

    If I put:

    Medium and big tables: (4 Million)
    - update statistics medium (all columns)

    Hight to small tables: ( < 120.000)
    - update statistics high (all columns )

    Can I got best performance using that statistics ?

    What do u think..

  5. #5
    Join Date
    Apr 2007
    Location
    Jundiai / SP - Brasil
    Posts
    311
    This is very hard to say, this can variable in each environment.

    but, my personal opinion, this is almost ok, missing only the update statistics low for all tables first , and the update statistics HIGH to all head index columns
    Tip, when you put the update statistics , if no user are using the database, use the SET PDQPRIORITY 100 , and review your configurations of PDQ on your ONCONFIG. This will boost the time execution from your update statistics
    ________________________________________
    César Inacio Martins
    Jundiai / SP - Brasil
    http://www.imartins.com.br/informix - em Português
    http://www.imartins.com.br/informix - English (translated by Google).
    ________________________________________

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •