RE: Any performance benefits in going to db_16k_cache_size or db_32k_cache_size

Contrary to what some authors have stated about using a larger block
size I am of the opinion that there is generally little to no
performance benefit to using 16k or 32k block sizes on most systems
especially when you can into consideration the increased concurrent
update activity that can end up directed to the same block.
 
From chapter 4 Memory Structures of his book, Expert Oracle Database
Architecture, Tom Kyte says, "multiple blocksizes were not intended as a
performance or tuning feature, but rather came about in support of
transportable tablespaces" (p 147).
 
It you really know what you are doing (understand the application and
data) I am sure the feature can be put to good use in some cases, but
overall I think this is a feature that should be used with caution.
 

-- Mark D Powell -- 
Phone (313) 592-5148 

 


________________________________

        From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Abhay Suresh
Kulkarni
        Sent: Wednesday, January 10, 2007 3:05 AM
        To: arunchakrapanirao@xxxxxxxxx; oracle-l@xxxxxxxxxxxxx
        Subject: RE: Any performance benefits in going to
db_16k_cache_size or db_32k_cache_size
        
        

        > I was trying to do some bench marking here for one of the
queries with 8,16 and 32k index tablespaces.

        > All I am seeing is the logical reads going down by half but
the elapsed time for these queries are still the same.

         

        For operations like nested loop, PIO may go down by 2 but LIO
will be same. As far as timing of queries is concerned, tune it to use
better access paths if any.

         

        Collecting histograms with appropriate bucket size will to the
trick for many a bad queries.

         

        Rgds

        Abhay

         

        Manhattan Assoicates

        Phone: 40418080 Ext: 4635

         

        -----Original Message-----
        From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of arun chakrapani rao
        Sent: Wednesday, January 10, 2007 10:10 AM
        To: oracle-l@xxxxxxxxxxxxx
        Subject: Any performance benefits in going to db_16k_cache_size
or db_32k_cache_size

         

        Hi all,

        I am currently working on a 1.5T DSS running on 8k blocksize.

        This db is 90% of the time doing sequential reads.

        Was wondering if we go for a 16k or 32k blocksize just on index
alone

        would there be any benefits in performance.

        Has anybody impletemented this and seen any performance
benefits,

        Please do share your experience.

        I was trying to do some bench marking here for one of the
queries with

        8,16 and 32k index tablespaces.

        All I am seeing is the logical reads going down by half but the

        elapsed time for these queries are still the same.

        Now what am i missing?

        Please do share your thoughts.

         

        -- 

        thanks in advance.

        Arun

        --

        http://www.freelists.org/webpage/oracle-l

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