Pablo - You may be able to find some of the answers in Oracle and the O.S.
- What does the O.S. I/O stats look like when you see this situation. Are
the disks about to burn off the spindles? Or are they sitting idle?
- What do the Oracle Wait statistics look like? What are the 3 big wait
times
Dennis,
Thanks for your answers and your time.
I was interested in how the OS (Sun, AIX, HP, etc)
classifies the CPU time used by the processes.
Taking a look at the WAIT I/O statistic taken with
sar -u I started wondering what they really meant:
ie
%usr %sys %wio %idl
30 5
sar may be installed from the Additional Installation CD of Tru64 Unix .
you are correct that does NOT come with the Default installation
-Original Message-
Sent: Friday, October 11, 2002 3:19 AM
To: Multiple recipients of list ORACLE-L
Pablo - Well, you've passed beyond my expertise,
Pablo
What does your I/O look like while %wio is high? Specifically, I would
suggest:
- Look at the disk subsystem I/O, is it experiencing a high rate of I/O?
- Run STATSPACK and see which tablespaces are "hot".
- Are a lot of table scans being executed?
Dennis Williams
DBA
Lifetouch, Inc
First a minor correction: sar -u has %wio and not sar -q.
Now, %wio reports the % of the time the CPU was idle while processes, that
otherwise would have run, waited for the outstanding I/O requests to
complete.
I believe the next few sentences in the book shed more light on %wio and
attempt to
Pablo - Another idea. Enter "man sar" at your command line. Here is the
paragraph from the Solaris manual. Hope this helps.
-uReport CPU utilization (the default):
%usr, %sys, %wio, %idle
portion of time running in user mode, running in
syste
Pablo - Well, you've passed beyond my expertise, and I can't really add any
more. Someone else may reply that is knowledgeable on these issues. Other
than that, you may want to find a list devoted to the operating system you
are on. In my admittedly meager experience, this tends to be somewhat
ven
Dennis:
Thanks for answering, what do you mean by, or may
be what do you think Gaja means by:
"He points out that the Solaris sar -q command has a
"%wio" column, a measure of processes that are
currently using the CPU, but are waiting for I/O
requests to be serviced and hence are not making
p
Dennis:
Thanks for answering, what do you mean by, or may
be what do you think Gaja means by:
"He points out that the Solaris sar -q command has a
"%wio" column, a measure of processes that are
currently using the CPU, but are waiting for I/O
requests to be serviced and hence are not making
p
Pablo - I posted the following paragraph yesterday:
3) I looked in Oracle Performance Tuning 101 to see what Gaja has to say.
He points out that the Solaris sar -q command has a "%wio" column, a measure
of processes that are currently using the CPU, but are waiting for I/O
requests to be service
Hi list
Can anyone explain me what exactly does the WAIT
I/O column of the sar -u output mean?
Does it represent the % of CPU used by the kernel
processes to perform I/O?
As far as I know the waiting processes do no wait
actively when they ask for an I/O. right? The OS uses
the SLEEP a
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