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Home -> Community -> Usenet -> c.d.o.server -> Re: Tuning DB_BLOCK_BUFFER
A copy of this was sent to "Winnie Liu" <oracle_dba_at_zdnetmail.com>
(if that email address didn't require changing)
On Tue, 15 Sep 1998 19:40:37 -0700, you wrote:
>HI everyone,
>
>Is it going to hurt the database performance if I increase the number of
>DB_BLOCK_BUFFER to a large number? I am absolutely sure that the RAM and
>SHMMAX parameter is set in a way that it is big enough for the whole SGA to
>settle in. And the Oracle Version is 7.3.4.0.1 on Solaris 2.5.1. The cache
>hit ratio used to be 78%. I tried to increase it to 80s by increasing the
>number of DB_BLOCK_BUFFER. So the whole area of SGA goes from 185MB to 190MB
>(not too big for a normal database). ANd then the cache hit ratio dropped to
>around 40%!!!!
>
how long was the database running when you grabbed the 78% number? Did you leave it running that long before you grabbed the 40% number? Cache Hit ratio is majorly impacted by time. After you start up, you cache hit is typically terrible but over the course of a day, a week, an so on, it will level out.
5 meg added to db block buffers is not very significant.
>I know that you can set the db_lru_extended_statistic (or something similar)
>to check the the performance increase for each addition of db_block_buffer.
>But since that database is in production for 24*7. There is no way I can
>shutdown the database and check for it. Does anyone have any idea why this
>is the case?
>
>I also checked the paging and swapping and the CPU utilization on the box,
>everything look normal.
>ANd since we have application running on that database, the transactions are
>more or less the same daily.
>
>Thanks very much
>
>Winnie
>
Thomas Kyte
tkyte_at_us.oracle.com
Oracle Government
Herndon VA
--
http://govt.us.oracle.com/ -- downloadable utilities
Anti-Anti Spam Msg: if you want an answer emailed to you, you have to make it easy to get email to you. Any bounced email will be treated the same way i treat SPAM-- I delete it. Received on Wed Sep 16 1998 - 09:18:33 CDT
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