Re: Oracle memory allocation on Linux 2.6

On Wed, 02 Apr 2008 03:20:27 -0700, vitalisman wrote:

On 9i, filesystemio_options=none (default) and Oracle binaries are not
linked for AIO (default, at least with RAC). I'm in the process of
testing AIO and DIO on RAC 9i following Oracle support questions, but
the first attempts gave way to some instance internal errors... I've
asked the support if this is really a supported configuration (at least
with OCFS1, it was not, apparently.)

Thanks Mladen for your answer!

Jerome, direct I/O should lower memory consumption simply because it
bypasses buffer cache over which we have no control. you still can control
the amount of consumed memory through

- min_free_kbytes,
- dirty_background_ratio,
- dirty_expire_centisecs
- dirty_writeback_centisecs.

You cannot control the size of cache components (like buffer cache) but
you can control behavior and overall limit with min_free_kbytes. It's
essentially the same approach as the one taken by oracle. You can
determine an overall lump of memory that you want to use, but not the
structure of that lump. The structure will be adjusted by some AI
predictive component of the software. So far, the "I" part is failing
miserably in both cases. With Linux, I really have a problem with the
"OOM killer" component. I cannot see how would that be superior to the
traditional mechanisms for fine-tuning the memory allocation. I used to
work on an ancient and arcane OS, the best one I've ever seen, called
"VAX/VMS". I started with the version 4.2 and the last version that I used
was 5.5-2. Believe it or not, VAX/VMS used to have far superior monitoring
tools and memory tuning mechanisms to any of modern Unix systems. Linux
systems are far inferior to things like AIX 5.3, HP-UX 11.11 or Solaris
10 and those systems are, in turn, far inferior to VAX/VMS.
I believe that the root of the evil is in the crusade against expensive
administrators. DBA personnel, as well as system administrators are
considered "expensive" and disliked by the modern management. Just as
there is a tendency to cut the number of expensive workers in automobile
industry, there is also a tendency to replace everybody by "business
professionals", people programming with Hibernate and Tapestry for
WebLogic or JBoss, knowing next to nothing about databases or the
underlying OS. That's the real spirit of Windows platform, as well as the
Linux platform. If I understand the business correctly, what is wanted is
the system that can be used and administered by Elbonians. Fortunately for
us, the effect is precisely the opposite. Oracle11 is the most complex
database to date and Linux 2.6 is the most problems-prone Linux version
ever. You need better administrators than ever, fewer and fewer are up to
the task. I will not shed a tear over a demise of Linux, when that
happens. However, don't be mistaken: the industry will succeed,
eventually. They succeeded in the automobile industry, there is no reason
to doubt the progress and the prospect of the ultimate victory for idiots.
HAL 9000 awaits us.

--
Mladen Gogala
http://mgogala.byethost5.com
.

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