Does Select uses DB_buffer_cache?
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Thread: Does Select uses DB_buffer_cache?

  1. #1
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    Does Select uses DB_buffer_cache?

    Hello:

    Just curious to know, if Select statement with full tablescan (No indexes are used or not existing based on CBO) uses db_buffer_cache?

    If the table is indexed and if server process using indexes to fetch data then, definitely it has to use db_buffer_cache? Isnt it?

    Thanks, ST2003

  2. #2
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    Does Select uses DB_buffer_cache? Do we need air to breathe?

    You can't get anything out of oracle database that hasn't been read out of buffer cache. No matter if your query uses indexes or does a FTS, no matter if it need to perform any physical read or not, every single row that it returns to you is read from buffer cache.
    Jurij Modic
    ASCII a stupid question, get a stupid ANSI
    24 hours in a day .... 24 beer in a case .... coincidence?

  3. #3
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    I'm unclear on exactly what your question is, but if any of the blocks of the table are available in the buffer then they will be read from it, not from disk -- if they are not available in the buffer then they will be read into it.

    You would probably benefit from a cover-to-cover read of the concepts guide -- it would give you a very solid grounding in many of these detailed "how does Oracle do that" issues .
    David Aldridge,
    "The Oracle Sponge"

    Senior Manager, Business Intelligence Development
    XM Satellite Radio
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    Oracle ACE

  4. #4
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    what you need is RTFM

  5. #5
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    Thanks Guys.. I know this for sure.. but the lead dba in my company confused me and I just kept quiet. I did not argue and I checking with you guys..

    Client process submits request to server process
    server process takes it to the db buffer cache
    transaction starts-all locks get applied automatically
    throws into RBS, if DML
    Data is processed in DB Buffer Cache, based on the DML and exec path.
    After Parse, Exec and fetch is done.. by server proc to user process.
    If Update or Delete, then it also gets to RedoLog buffers..

    I was expecting an Yes/No but I get the point..

    ST2003

  6. #6
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    Originally posted by st2003
    Thanks Guys.. I know this for sure.. but the lead dba in my company confused me and I just kept quiet. I did not argue and I checking with you guys..
    I think your Senior/Lead DBA needs..

    Originally posted by pando
    what you need is RTFM
    funky...

    "I Dont Want To Follow A Path, I would Rather Go Where There Is No Path And Leave A Trail."

    "Ego is the worst thing many have, try to overcome it & you will be the best, if not good, person on this earth"

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