RE: low blocks/read on temp
- From: John Kanagaraj <john.kanagaraj@xxxxxxx>
- To: "'Brandon.Allen@xxxxxxxxxxx'" <Brandon.Allen@xxxxxxxxxxx>, Dave.Herring@xxxxxxxxxx, "Oracle-L@Freelists. Org (E-mail)" <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 26 Jul 2005 15:58:47 -0700
Dave,
Just wondering how you measured the avg blocks per read (I might be too
dense and missed something...) In any case, the largest I/O that the OS can
service is determined by the 'maxio' parameter (or its equivalent in Tru64).
Normally, this is 64K, but I believe this can be tweaked up to 1MB. So, even
if you set a unnaturally high DBFMBRC, the OS will limit what it provides
back... Steve Adams has a script at his site that measures the actual
DBFMBRC, but I belive that goes against non TEMP data...
Hth,
John Kanagaraj <><
DB Soft Inc
Phone: 408-970-7002 (W)
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From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]
On Behalf Of Allen, Brandon
Sent: Tuesday, July 26, 2005 3:33 PM
To: Dave.Herring@xxxxxxxxxx; Oracle-L@Freelists. Org (E-mail)
Subject: RE: low blocks/read on temp
Hi Dave,
I just checked a few of my databases and the highest was 7 blocks per read,
the lowest was 1.9. Why would you expect it to be so high? I believe the
blocks per read for TEMP is a function of your
db_file_multiblock_read_count, extent sizes, and cached blocks, just like
with any other tablespace. Not sure if this is correct though since I think
TEMP is usually read with direct reads (bypassing the buffer cache) and I'm
not sure if direct reads determine their blocks/read the same way as regular
db_file_sequential/scattered_reads.
Regards,
Brandon
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On
Behalf Of Herring Dave - dherri
Sent: Tuesday, July 26, 2005 3:09 PM
To: Oracle-L@Freelists. Org (E-mail)
Subject: low blocks/read on temp
Has anyone run into situations where the avg blocks per read against their
temporary tablespace seemed extremely low? We have a database block size of
32K, yet I'm seeing blocks per read on TEMP 5.2, on average. I would expect
much, much higher, at least in the 20's. Is this a realistic expectation?
I'm running 9.2.0.4 on Tru64 5.1.
Thanks.
Dave
-------------------------------------
Dave Herring, DBA
Acxiom Corporation
3333 Finley
Downers Grove, IL 60515
wk: 630.944.4762
< <mailto:dherri@xxxxxxxxxx> mailto:dherri@xxxxxxxxxx>
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