Be Prepared with Baselines

  • Steve Jones - SSC Editor

    SSC Guru

    Points: 714311

    Comments posted to this topic are about the item Be Prepared with Baselines

  • MattF

    SSCrazy

    Points: 2280

    I agree baselines are critical. SQL server's inbuilt data collections also provide a mechanism for accessing performance metrics over time. Together with Reporting Services report subscriptions, we use this to monitor all of our internal databases as well as those of our remote customers.

  • Jeff Moden

    SSC Guru

    Points: 993770

    Heh... I wonder how many people actually know how bad their system currently is when they take that first baseline.  I also wonder if they actually do anything about it to improve it.  😀

    "Hey Mister!!!  Do you realize you have a bear trap closed on your groin????"
    "Yep... that's my baseline."

    --Jeff Moden


    RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
    First step towards the paradigm shift of writing Set Based code:
    ________Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
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    When you put the right degree of spin on it, the number 3|8 is also a glyph that describes the nature of a DBAs job. 😉

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  • TomThomson

    SSC Guru

    Points: 104707

    Jeff Moden - Monday, June 11, 2018 8:31 PM

    Heh... I wonder how many people actually know how bad their system currently is when they take that first baseline.  I also wonder if they actually do anything about it to improve it.  😀

    "Hey Mister!!!  Do you realize you have a bear trap closed on your groin????"
    "Yep... that's my baseline."

    Sure, there are probably people who make that mistake.  But I suspect they are a minority.  The proper assumption is that the first baseline is meaningless (as are, probably, the next few).

    My approach is that  I measure things several times, and get a baserange rather than a baseline.  Then I change something a bit, and see if the measure goes outside the base range - and if it goes somewhere I think is better, that tells me my change may be useful - but not whether the amount of change is enough or too much or too little so I have to take measures with a lot of changes in that dimension. If it goes the wrong way, then I need to see whether a smaller of larger change would go the right way.  Then I change some other thing, and the process is similar.  There are probably lots of things to change, and in the end changing one at a time isn't enough, so one has to end up with an N-dimensional table of results if there are N things one might change.  Doing this properly requires a very large amount of measuring.  So it may well be an unacceptable overhead.  So I need to find some things that I understand (for example that if f I usually want to sort on X then having an index on X has a chance of being useful), and if I can find enough things that I understand then I can reduce the amount of measurement (perhaps partly by reducing the number of dimensions I have to consider)  to get a reasonable conclusion at a lower cost than blind experimentation..

    Tom

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