Re: Books or links on Oracle Wait events (in depth)
- From: Kevin Closson <ora_kclosson@xxxxxxxxx>
- To: cary.millsap@xxxxxxxxxxxx, shastry17@xxxxxxxxx
- Date: Fri, 8 Oct 2010 09:43:22 -0700 (PDT)
Just a small nit.
The mappings of scattered read and db file sequential read varies based on a
certain factors. If, for instance, you are on a file system the mappings vary
based on the setting of filesystemio_options (SETALL versus DirectIO versus
default), using character special datafiles, using ASM with ASMLib using NFS,
using DNFS.
The OSDs are actually quite complicated especially if you are supporting more
than one platform.
________________________________
From: Cary Millsap <cary.millsap@xxxxxxxxxxxx>
To: shastry17@xxxxxxxxx
Cc: oracle-l <oracle-l@xxxxxxxxxxxxx>
Sent: Tue, October 5, 2010 4:43:33 AM
Subject: Re: Books or links on Oracle Wait events (in depth)
See also section 18 of
http://method-r.com/downloads/doc_details/10-for-developers-making-friends-with-the-oracle-database-cary-millsap
The best place to learn what the Oracle timed events mean is the strace (truss,
etc) manual page. Activate Oracle extended SQL trace an Oracle kernel (shadow)
process, and strace it at the same time. In your strace output, you can see the
Oracle kernel process's write() calls to its trace file. The syscall(s) that
occur preceding each write is what you look up in the strace man page. This is
how you learn things like (on my 10.2 instance on RHEL r3):
* A db file scattered read is an __llseek() call and a readv() call.
* A db file sequential read is a pread() call.
* An enqueue is a semtimedop() call.The *nix documentation for these
syscalls
is very clear, yet if you have any remaining doubts about what's going on, you
can even view the Linux source code for what these calls are doing and how they
do it.
Once you learn how the Oracle kernel interacts with its underlying operating
system, everything starts to fall right into place. It's just code.
Cary Millsap
Method R Corporation
http://method-r.com
http://carymillsap.blogspot.com
On Tue, Oct 5, 2010 at 5:34 AM, Chris Dunscombe <cdunscombe@xxxxxxxxx> wrote:
I'll second the book recommendation. It's a great book and the best I've seen
on
the subject.
>
>Chris
>
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________________________________
From: kyle Hailey <kylelf@xxxxxxxxx>
>To: bdbafh@xxxxxxxxx
>Cc: shastry17@xxxxxxxxx; oracle-l <oracle-l@xxxxxxxxxxxxx>
>Sent: Tue, 5 October, 2010 5:03:13
>Subject: Re: Books or links on Oracle Wait events (in depth)
>
>
>
>I'll second what Paul said
>
>
>and if you still want to learn about the waits, I've put up a bunch of non-RAC
>wait documentation at
>https://sites.google.com/site/embtdbo/wait-event-documentation
>The only decent book I'm aware of is The Oracle Wait Interface, see on
>Amazon http://tinyurl.com/2ck8nc4
>
>
>The Oracle documentation itself has gotten better over the years
>
>
>Best Wishes
>Kyle Hailey
>http://db-optimizer.blogspot.com/
>
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>>
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