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 simplify it further... - Kirti -----Original Message----- Sent: Thursday, October 10, 2002 4:19 PM To: Multiple recipients of list ORACLE-L 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 prudent use of the CPU" How can the processes be using the CPIU if they are waiting for some I/O requests? What I'm trying to say is that that can't consume CPU cicles if they are waiting (SLEEPING). Why does sar shows that these CPU cicles are used in waiting for I/O? Who's using them? TIA ---------------------------------------------------- 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 serviced and hence are not making prudent use of the CPU. He further says that %sys and %wio should be less than 10-15% and if it is consistently higher you need to get to the bottom of it, and usually it is a application causing the problem. No details on how to get to the bottom. Dennis Williams DBA Lifetouch, Inc. [EMAIL PROTECTED] -----Original Message----- Sent: Thursday, October 10, 2002 3:16 PM To: Multiple recipients of list ORACLE-L 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 and WAKEUP primitives. So, Which process is using this CPU? (The WAIT I/O%) Or does this WAIT I/O have to be taken as if the CPU were idle? Please shed some light on this. Thanks _______________________________________________________________ Yahoo! Messenger Nueva versión: Webcam, voz, y mucho más ¡Gratis! Descárgalo ya desde http://messenger.yahoo.es -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: =?iso-8859-1?q?Pablo=20Rodriguez?= INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Deshpande, Kirti INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
