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Thread: Slow?

  1. #1
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    Unanswered: Slow?

    Hi,
    I am working for a customer who has a 60gb tablespace and 40gb index tablespace - both of which are nearly full of data. There are only two major tables in the tablespaces.

    The index's seem to be set up ok and I don't think that is why it is so slow- i think it is a hardware issue.

    The hardware running this system is;
    DEC Alpha 500mhz
    512mb ram
    2x4.3gb system discs
    110gb external SCSI RAID array

    oh, also Windows NT Alpha

    It is running oracle 7.3.

    There is alot of inserts/selects/deletes occuring all the time.

    Should I recommend a hardware/software upgrade?

    Could the tablespaces be very fragmented? How can I tell? How can I defragment it?

    Thanks!

  2. #2
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    Re: Slow?

    Before giving any recommendations you have to :

    1. Check waits events of your database
    2. Check how your hardware resources are utilized by using OS
    monitoring tools

    After collecting and analyzing the above mentioned information you would be able to decide if your hardware is adequate to your needs.

    Concerning fragmentation of tablespaces there are plenty of scripts and applications you may use to get this information.

  3. #3
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    Hi,
    I have done the second item on your list and the disc queue is always full during use, and processor is at about 25%. From this I guess my bottleneck is in disc bandwidth. Is this correct, or should I check other things too?

    I have no clue about the first item, checking wait events. Is this information got from v$sysstats?

  4. #4
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    1. Looks like you are right, but also check how load is distributed
    among your disks
    2. v$system_event, v$waitstat, v$sysstat, v$sesstat but better use such
    tools as oracle performance diagnostic tool - STATSPACK or simple
    bstat/estat. You can also use other performance diagnostic tools.

  5. #5
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    Thanks!

    only the disc with oracle datafiles is being thrashed. They are all on the same array...

    any suggestions on improving performance and what kind of machine to go for?

  6. #6
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    Originally posted by rhs98
    Thanks!

    only the disc with oracle datafiles is being thrashed. They are all on the same array...

    any suggestions on improving performance and what kind of machine to go for?
    What RAID level is implemented there ? (0,1,5,10)

  7. #7
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    raid 5 i belive...

    it has 14x9.1gb discs
    Last edited by rhs98; 06-19-02 at 04:15.

  8. #8
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    I guess this is the problem. It is recommended to avoid RAID 5 on systems with high volume of inserts/updates. I think you should consider
    the possibility to reorganize your disks in RAID 10. It may greatly alleviate the problem. And if you do this do not forget to choose the correct stripe-width value.

  9. #9
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    this however would involve purchasing more discs or sacrificing some space, no?

    How many extra discs would I need?

  10. #10
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    Originally posted by rhs98
    this however would involve purchasing more discs or sacrificing some space, no?

    How many extra discs would I need?
    Well that's very easy to count. If you have 14x9.1gb disks available, it means that you would only have 7x9.1gb disks for your data (if you decide on RAID 10).

  11. #11
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    would this provide a good performance gain for the money?

    If the array [Dec storageworks de450] cannot take more discs, does anyone know of a good external raid array to buy?

  12. #12
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    RAID 10 is supposed to provide the better performance for I/O intensive applications (especially for inserts/updates) than RAID 5. In your case it is likely that you will get a sufficient performance gain.
    As to the external raid - consider SPARCstorage Arrays, it may be integrated with different platforms and OS.

  13. #13
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    ok thanks dmitry will look in to what you suggested

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