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Thread: indexes and I/O

  1. #1
    Join Date
    Feb 2007
    Location
    India
    Posts
    56

    Unanswered: indexes and I/O

    Hi,
    If i enable 16 K I/O before creating indexes. Will creation of indexes use this feature. If we have any bad effects for other processes please let me know.

    Thanks inadvance.

    VVS Naveen Pabolu.
    Regards,
    Naveen.
    Sybase DBA-Consultant

  2. #2
    Join Date
    Mar 2007
    Posts
    72

    index creation

    Hi Naveen,
    Assuming your default page size is 2k, having 16 K pool does give you benefits whilst attempting to create indexes etc. Say you have 2000 MB of default_data_cache, and you have no 16 K pool, try creating a 16 K of size say 1600 MB and then do index creation, run sp_sysmon '00:10:00' for example and monitor the output, you will see that large i/o usage more than 90%. this is because, sybase can then use 16 K i/o instead of 2 k i/o so a single disk i/o fetches 8 times more data than 2 k i/o resulting in reduced disk i/o thereby improving performance.

    Hope this helps

    suda

  3. #3
    Join Date
    Feb 2007
    Location
    India
    Posts
    56

    Re: Indexes and I/O

    Hi Suda,
    Thanks for your valuble suggestion. I have enabled 16 K I/o as per your suggestions. My dafault data cache is 2000 MB only so i have enabled 16 K I/o and i started creating clustered index and i have observed showplan it is showing 2 K I/o only not 16 K I/o. Is there any thing wrong here? Please advise.
    Regards,
    Naveen.
    Sybase DBA-Consultant

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