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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Tune for 'db file sequential read'
Hi Deepak,
The db file sequential read usually ndicates wait for sequential block reads
(indexes mostly). Check to see if you have any buffer busy waits and if
there are buffers that is being contended upon. You can query the x$bh
segment to determine the blocks being waited upon and then determine the
segments these blocks belong to.
You can try to alleviate the contention for these blocks by caching them
using buffer pool feature if you are in 8.0 and above. Also check to see if
there are lot of free buffer waits which might indicate increase in db
buffers is needed.
Regarding the size of the SGA, it depends on what else is going on at the
same time in instance A and instance B. The process might not be contending
for any resources on instance B but on A some other process might be
contending for the same resources.
I am sure you would have done this already, make sure that the execution plans match for the queries and if using CBO check if the stats are up to date on instance A.
Hope this helps.
Regards,
Madhavan
IBM Corporation Webserver Div
>From: Deepak Sharma <sharmakdeep_at_yahoo.com>
>Reply-To: ORACLE-L_at_fatcity.com
>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>Subject: Tune for 'db file sequential read'
>Date: Wed, 03 May 2000 10:06:34 -0800
>
>On querying the v$session_event, I could see one
>process taking a very large wait time. The process
>takes about 4 Hrs to complete on *this* instance (A),
>whereas it takes a few minutes on another instance(B)
>with almost same amount of data. The Metalink pages
>suggest to test by increasing DB_BLOCK_BUFFERS, but
>the interesting thing is that instance A's SGA is
>128M, whereas instance B's is 44M. Any suggestions ?
>
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>Author: Deepak Sharma
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>
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