Re: formulas for correct sizing of various parameters

Hi

The block size you choose should be a multiple of the OS block size, otherwise reads and writes of Oracle blocks could / would cross OS block boundaries. The block size you choose depends on the type of database and applications you have ie OLTP. In batch processing for instance where you have large amounts of data to process a larger block size is better and a large db_block_buffers, as the data you need will tend to be in the SGA more, reducing disk reads. For OLTP where random reads occur a smaller block size is better to reduce the read times and the amount of data stored in the SGA that is not likely to be needed. ie users could read data from anywhere in OLTP, in batch processing the data is likely to be read in some sort of order and processed in some sort of order. Just picking a general size such as 8k as Steve Adams suggests might work in most occasions, but in larger systems choosing the correct block size can make quite a difference in performance.

In view of the above, I cannot see easily how one formula can be used.

just my two penneth

cheers

Pete Finnigan
www.pentest-limited.com

In article <3B8D37BC.5B72B7FB_at_mitre.org>, David Wilburn <dwilburn_at_mitre.org> writes
>I've got plenty of books and documents that all say that specifying
>correct values for initial/next/max extents, db_block_size, etc., are
>all critically important. However, I've yet to find any formulas
>specifying how to come up with the correct values.
>
>I've read that (at least of solaris) the block size should be some
>multiple of the output of the command 'pagesize' (in this case, 8KB),
>but I'm not sure whether it should be 8KB, 16KB, etc. Which should it
>be?
>
>How do I calculate appropriate values for initial/next/max extents?
>
>We're getting a new system in shortly, and I'll have the opportunity to
>rebuild our DB, so I'd like to get things right the first time.
>
>-Dave Wilburn

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