Re: DB_BLOCK_SIZE and Digital UNIX with AdvFS

On Mon, 12 May 1997 18:21:56 -0500, Robert Lowe <Robert.H.Lowe_at_lawrence.no.spam.edu> wrote:

>Hi!
>
>I'm not a DBA, so go easy on me! ;-) One of the tuning tips I've run
>across indicates that it is best to make DB_BLOCK_SIZE at least as large
>as the file system buffer size, if not a larger multiple of it. It's my
>understanding that AdvFS uses 8 KB "pages" which would seem to indicate
>that I should use at least an 8 KB DB_BLOCK_SIZE. Is this reasonable
>for a small-medium sized dB, and what might be the ramifications of
>using a block size this large? I understand that I'll have to
>correspondingly reduce DB_BLOCK_BUFFERS to reduce the size of the SGA to
>avoid memory problems. How much inefficiency is introduced by using a
>smaller DB_BLOCK_SIZE? Or can one do this at all?
>
>I realize I'm not providing a lot of detail (the application is OGF, if
>that helps a bit), so I don't expect a fully detailed response, but if
>there are others of you using AdvFS, I'd be interested in hearing how
>you approached this.
>
>TIA,
>Robert

The only time that the larger block size my impact you is if your system consists of lot of small tables. Then you may be getting more blocks than needed. Given the size of tables on systems such as PeopleSoft, Oracle Financials, etc, the size of those tables are big enough to utilize the larger block size. I have seen system performance dramatically improve just by changing the block size (and reducing the db_block_buffer). I do not have any benchmarks , but The larger the block size, the less time Oracle has to spend going to the disk to get data. The same goes for writing, redo etc...

Hope this helps

sheilah scheurich
DBA
scheuric_at_sprynet.com Received on Wed May 14 1997 - 00:00:00 CDT