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Thread: Latch Time

  1. #1
    Join Date
    Nov 2003
    Location
    Akld, NZ
    Posts
    38

    Arrow Unanswered: Latch Time

    Hi All,

    This might be a bit of a question like "how long is a peice of string" however here goes.....

    What is considered to be a high average latch time?

    We have a SQL2000 machine which has:
    700-900 ms average latch time
    100% Buffer Cache Hit Ratio
    No memory pages / second
    Very low (almost always below 5%) cpu usage
    Next to no disk transfers / sec
    0 average lock time

    I am surprised that the latch time is so high. Any ideas, whether I should be looking at something in particular?

    Cheers in advance.
    Troy
    Sideways see's more scenery

  2. #2
    Join Date
    Nov 2003
    Location
    Akld, NZ
    Posts
    38
    Anyone - please?
    Sideways see's more scenery

  3. #3
    Join Date
    Apr 2004
    Location
    Kansas City, MO
    Posts
    734
    It really is kind of a hard question to answer. A high latch time generally points to a memory shortage and has a direct correlation to a low buffer cache hit ratio. Since your buffer cach hit ratio is 100%, you obviously don't have a problem with that.

    The other thing it can point to is needing more I/O width on your disk subsystem. That's pretty doubtful again with that high of a buffer cach hit ratio. You might want to look at your physical read and write cache to see what those counters are at.

    Really though, it doesn't seem to me you have any problems and I wouldn't worry about the 700-900ms average latch time. If you see that number rising dramatically when a load gets put on the system, you need to come back and add to this post so we can look at it. Otherwise, I wouldn't worry about it, especially if your system seems to be running fine and getting the desired response times from the database server.

    Hope this helped.
    MeanOldDBA
    derrickleggett@hotmail.com
    When life gives you a lemon, fire the DBA.

  4. #4
    Join Date
    Nov 2003
    Location
    Akld, NZ
    Posts
    38

    Thumbs up

    Thanks for the response!! Yeah that is pretty much what I had thought - but was after some confirmation from others.
    Had a feeling it was slow disk/issues with I/O, so will keep an eye on it and if it causes any more concern, I will post back.

    Thanks again!
    Troy
    Sideways see's more scenery

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