RE: Oracle internal flaws?
- From: D'Hooge Freek <Freek.DHooge@xxxxxxxxx>
- To: "jslowik@xxxxxxxxx" <jslowik@xxxxxxxxx>, "Mark.Brady@xxxxxxxxxxxxxxxxx" <Mark.Brady@xxxxxxxxxxxxxxxxx>
- Date: Tue, 15 Mar 2011 15:44:13 +0100
ASM are in fact raw devices.
The ASM instance is providing the processes a kind of "mapping", but it are the
server processes themselves which are doing the reads (and writes in case of
dbwr \ lgwr processes).
Also, even on "normal" filesystems you can indicate that oracle has to use
directio which will bypass the filesystem buffer cache.
Regards,
Freek D'Hooge
Uptime
Oracle Database Administrator
email: freek.dhooge@xxxxxxxxx
tel +32(0)3 451 23 82
http://www.uptime.be
disclaimer: www.uptime.be/disclaimer
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From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Joel Slowik
Sent: dinsdag 15 maart 2011 15:35
To: Mark.Brady@xxxxxxxxxxxxxxxxx
Cc: oracle-l@xxxxxxxxxxxxx
Subject: RE: Oracle internal flaws?
This stuck out to me:
"Especially noteworthy, because it uses file system files (not raw partitions),
and the "caching" is outside, it relies heavily on (and is very sensitive to)
the file system cache that you have set up. likewise, Oracle needs a massive
amount of memory for these processes."
That's true if you are using ASM or the file system to manage data files. When
creating a database, you can specify to oracle to use raw partitions as a
storage mechanism.
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Brady, Mark
Sent: Tuesday, March 15, 2011 10:09 AM
Cc: oracle-l@xxxxxxxxxxxxx
Subject: Oracle internal flaws?
I saw this answer today on StackOverflow.
http://stackoverflow.com/questions/5307590/cpu-usage-of-oracle-installed-database-machine
Quote from PerformanceDBA, a notable Oracle basher.
"Oracle does not have a true server architecture (others have it). Rather than
performing classic server tasks, such as multi-threading, caching of data
pages, parallel processing (split a query across many devices) etc. within
itself, it uses the o/s to do all that. That means for each user process
(PL/SQL connection) there is one unix process; 1000 users means 1000 unix
processes, all competing for the same resources.
Especially noteworthy, because it uses file system files (not raw partitions),
and the "caching" is outside, it relies heavily on (and is very sensitive to)
the file system cache that you have set up. likewise, Oracle needs a massive
amount of memory for these processes."
I'm not enough of an internals guy to accurately refute these declarations. Can
anyone help me understand which of these statements are true and whether or not
they are deficiencies?
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