That would appear to be sound reasoning. Be aware
that high values result in lower costs for full table
scans - which can give optimizer plans which are not
desirable.
You may also want to tweak some of the 'optimizer_'
prefixed parameters if you find too much scanning
going on.
hth
connor
- Jeff Wiegard <JWIEGARD_at_ngwmail.des.state.mn.us>
wrote: > Hi.
>
> I was hoping for some confirmation here.
>
> I'm running 8.0.5 on Solaris 2.7, with block size
> set to 8192.
> There is no 'maxphys' parameter in /etc/system.
>
> After some testing, I've decided to set the
> db_file_multiblock_read_count = 24, based on the
> following:
>
> 1. SQL> alter session set
> db_file_multiblock_read_count = 1000;
>
> 2. select value from v$parameter where name =
> 'db_file_multiblock_read_count';
>
> This gave me a value = 128
>
> 3. alter session set events '10046 trace name
> context forever,
> level 8';
>
> 4. select /*+ FULL(t) */ count(*) from sys.source$
> t;
>
> The trace file gave me the following:
>
> WAIT #1: nam='db file scattered read' ela= 0 p1=1
> p2=660 p3=25
> WAIT #1: nam='db file scattered read' ela= 0 p1=1
> p2=1167 p3=25
> WAIT #1: nam='db file scattered read' ela= 0 p1=1
> p2=1207 p3=25
> WAIT #1: nam='db file scattered read' ela= 0 p1=1
> p2=1272 p3=25
> WAIT #1: nam='db file scattered read' ela= 0 p1=1
> p2=1312 p3=25
>
> So then setting db_file_multiblock_read_count to 24
> would be about
> right ... right?
>
> Thanks,
>
> Jeff
>
>
> --
> Please see the official ORACLE-L FAQ:
> http://www.orafaq.com
> --
> Author: Jeff Wiegard
> INET: JWIEGARD_at_ngwmail.des.state.mn.us
>
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Received on Mon Nov 19 2001 - 16:47:07 CST