RE: db file scattered/sequential read wait

We are running SAP and there is a hourly background job which runs SQL against dba_segmen and dba_extents. I believe the program name is SAPLSDO0. Anyway, my question is: why it never bring down our databases?

-----Original Message-----
From: Wolfgang Breitling [mailto:breitliw_at_centrexcc.com] Sent: Wednesday, June 16, 2004 1:21 PM
To: oracle-l_at_freelists.org
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_at_rsiz.com>:

> 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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