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Thread: Low EST_PGA_CACHE_HIT_PERCENTAGE

  1. #1
    Join Date
    Jan 2015
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    4

    Question Low EST_PGA_CACHE_HIT_PERCENTAGE

    Hi Friends,

    While analysing the AWR report of Oracle 11g, In PGA TARGET Advisory i found low est_pga_cache_hit_percentage at size_factor =1.

    If I increase the PGA_AGGREGATE_TARGET size will it improve the performance of the queries that accessing SORT/MERGE/HASH paths.

    or

    Should i found the queries accessing SORT/MERGE/HASH paths and tune them?

    Which will be preferred one. Will that application to Dataware-house also?
    please suggest.

    Thanks & Regards,
    Saranya

  2. #2
    Join Date
    Nov 2000
    Location
    Pittsburgh, PA
    Posts
    4,166
    What version of Oracle are you using and what operating system? Other than the
    PGA cach hit percent, are you seeing any performance issues?

  3. #3
    Join Date
    Nov 2000
    Location
    Pittsburgh, PA
    Posts
    4,166
    What version of Oracle are you using and what operating system? Other than the
    PGA cach hit percent, are you seeing any performance issues?

  4. #4
    Join Date
    Mar 2007
    Location
    Ft. Lauderdale, FL
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    3,555
    Saranya --

    Couple of questions and some task to do...

    1- Is this a Data Warehouse or an OLTP database? one of your comments suggest DWH.
    2- You said you are seeing low pga_cache_hit_percentage ... what's the value?
    3- How big is your current PGA?
    4- How big is your SGA?
    5- How much memory do you have in the host?
    6- Is there anything else running on this host other than this particular Oracle instance?
    7- Please run query below and post results...
    select
    round(pga_target_for_estimate /1024 /1024 Target_MB,
    estd_pga_cache_hit_percentage,
    estd_overalloc_count
    from
    v$pga_target_advice ;

    Thank you
    Pablo (Paul) Berzukov

    Author of Understanding Database Administration available at amazon and other bookstores.

    Disclaimer: Advice is provided to the best of my knowledge but no implicit or explicit warranties are provided. Since the advisor explicitly encourages testing any and all suggestions on a test non-production environment advisor should not held liable or responsible for any actions taken based on the given advice.

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