RE: db file scattered/sequential read wait
- From: "Mark W. Farnham" <mwf@xxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 16 Jun 2004 15:43:31 -0400
certainly correct. the query was not mine by the way, just the endpoint
fixup.
I gathered from the thread that the inquiry was from someone who had an
individual object getting seriously pounded on.
Excellent idea to keep an efficient map populated in the wee hours (aka
"load valley" for global operations)!
mwf
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of Wolfgang Breitling
Sent: Wednesday, June 16, 2004 2:21 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: RE: db file scattered/sequential read wait
Just a word of caution. You don't want to run this query every time you want
to
find out the object for a db file read. That alone could bring your system
to
its knees, especially if you have LMTs - and if not, why not? (those who
still
manage Oracle 7 and lower systems are excused).
I run something like that in the wee hours of the morning when there is
spare
capacity and load the response into a table indexed by file# and block#.
This
way I don't go after the catalog tables and the response is immediate. Sure,
I
risk missing the occasional block (hasn't happened yet) if the object went
into
a new extent after I ran my report.
Quoting "Mark W. Farnham" <mwf@xxxxxxxx>:
> I think you want a minus one in the second term.
>
> Let's see, if block_id = 1 and you read 8 blocks, then 1...9, is *not*
what
> you want, so yeah, (block_id+blocks-1)
> would tighten up that predicate.
>
> mwf
>
--
regards
Wolfgang Breitling,
Oracle 7,8,8i,9i OCP DBA; Oaktable member
Centrex Consulting Corporation
www.centrexcc.com
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