Comments on: Beyond Oracle Wait Interface – Part 2 http://blog.tanelpoder.com/2010/01/15/beyond-oracle-wait-interface-part-2/?utm_source=rss&utm_medium=rss&utm_campaign=beyond-oracle-wait-interface-part-2 Oracle, Exadata, Performance, Troubleshooting - Mobile Life and Productivity. Wed, 08 Feb 2012 08:03:50 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: The Oracle Wait Interface Is Useless - part 3a | Scale Abilities http://blog.tanelpoder.com/2010/01/15/beyond-oracle-wait-interface-part-2/comment-page-1/#comment-9000 The Oracle Wait Interface Is Useless - part 3a | Scale Abilities Fri, 11 Nov 2011 14:39:12 +0000 http://blog.tanelpoder.com/?p=553#comment-9000 [...] analysis and has written a great tool, snapper, for just this purpose. If you have not already read part two of this series, head over to Tanel’s blog now to catch up before [...] [...] analysis and has written a great tool, snapper, for just this purpose. If you have not already read part two of this series, head over to Tanel’s blog now to catch up before [...]

]]> By: The Oracle Wait Interface Is Useless Part One: The Problem Definition | Scale Abilities http://blog.tanelpoder.com/2010/01/15/beyond-oracle-wait-interface-part-2/comment-page-1/#comment-8999 The Oracle Wait Interface Is Useless Part One: The Problem Definition | Scale Abilities Fri, 11 Nov 2011 14:38:43 +0000 http://blog.tanelpoder.com/?p=553#comment-8999 [...] OK, so we are now just confirmed – we have a nasty query that is just using CPU and never waiting for anything. Let’s not start guessing at this stage what the problem is, let’s try and find out the real answer. At this stage, we might jump to v$sql_plan_statistics_all to find out what is going on. These statistics are only updated when statistics_level is set to ALL, and even then do not update until the statement is complete. In our little example here, the query is already running – we can’t set statistics_level=all, and we can’t wait until the query completes – it might never do so! Of course, it’s probably OK to get the user to kill the query and restart with statistics_level=all, or even the ctrl-c would allow the stats to update. However, let’s assume neither of those things are possible, as this is only an example case. So what techniques can we use to find the problem? One of them might be the new SQL Execution Monitoring in 11g (which looks very nice), if you have the required license – but that is a very specific case where the problem is a SQL execution problem. What if it is not a SQL execution problem? We need a more general method for finding the answer. That’s the subject of part two of this blog, over to Tanel for Part Two! [...] [...] OK, so we are now just confirmed – we have a nasty query that is just using CPU and never waiting for anything. Let’s not start guessing at this stage what the problem is, let’s try and find out the real answer. At this stage, we might jump to v$sql_plan_statistics_all to find out what is going on. These statistics are only updated when statistics_level is set to ALL, and even then do not update until the statement is complete. In our little example here, the query is already running – we can’t set statistics_level=all, and we can’t wait until the query completes – it might never do so! Of course, it’s probably OK to get the user to kill the query and restart with statistics_level=all, or even the ctrl-c would allow the stats to update. However, let’s assume neither of those things are possible, as this is only an example case. So what techniques can we use to find the problem? One of them might be the new SQL Execution Monitoring in 11g (which looks very nice), if you have the required license – but that is a very specific case where the problem is a SQL execution problem. What if it is not a SQL execution problem? We need a more general method for finding the answer. That’s the subject of part two of this blog, over to Tanel for Part Two! [...]

]]> By: The Oracle Wait Interface Is Useless – part 3b | Scale Abilities http://blog.tanelpoder.com/2010/01/15/beyond-oracle-wait-interface-part-2/comment-page-1/#comment-8998 The Oracle Wait Interface Is Useless – part 3b | Scale Abilities Fri, 11 Nov 2011 14:38:24 +0000 http://blog.tanelpoder.com/?p=553#comment-8998 [...] SQL, and that’s about all the information we have. As Tanel stated in his posting for Part Two, this is the stage where it makes good sense to dig into session-level statistics (not system-level [...] [...] SQL, and that’s about all the information we have. As Tanel stated in his posting for Part Two, this is the stage where it makes good sense to dig into session-level statistics (not system-level [...]

]]> By: Wojciech http://blog.tanelpoder.com/2010/01/15/beyond-oracle-wait-interface-part-2/comment-page-1/#comment-6301 Wojciech Fri, 28 Jan 2011 12:17:44 +0000 http://blog.tanelpoder.com/?p=553#comment-6301 Tanel, I am impressed by this doc and your style. Well done. One thing is not clear to me. I have always thought that when CPU is busy with logical reads and consistent gets there should be also many IO events in the meantime like 'db file sequential read'. They are just to put the blocks into SGA before it goes to CPU. I just wonder how is that possible that CPU works on logical reads continually for minutes and a single 'db file sequential read' doesn't happen. What exactly a 'logical read' on CPU is/does? I am just a begginer of oracle internals so would appreciate if you put some light on it. Tanel, I am impressed by this doc and your style. Well done.

One thing is not clear to me. I have always thought that when CPU is busy with logical reads and consistent gets there should be also many IO events in the meantime like ‘db file sequential read’. They are just to put the blocks into SGA before it goes to CPU. I just wonder how is that possible that CPU works on logical reads continually for minutes and a single ‘db file sequential read’ doesn’t happen. What exactly a ‘logical read’ on CPU is/does?

I am just a begginer of oracle internals so would appreciate if you put some light on it.

]]> By: The Oracle Wait Interface Is Useless (sometimes) – part 3b « James Morle's Blog http://blog.tanelpoder.com/2010/01/15/beyond-oracle-wait-interface-part-2/comment-page-1/#comment-3873 The Oracle Wait Interface Is Useless (sometimes) – part 3b « James Morle's Blog Thu, 18 Feb 2010 00:14:57 +0000 http://blog.tanelpoder.com/?p=553#comment-3873 [...] SQL, and that’s about all the information we have. As Tanel stated in his posting for Part Two, this is the stage where it makes good sense to dig into session-level statistics (not system-level [...] [...] SQL, and that’s about all the information we have. As Tanel stated in his posting for Part Two, this is the stage where it makes good sense to dig into session-level statistics (not system-level [...]

]]> By: Blogroll Report 08/01/2009 – 15/01/2010 « Coskan’s Approach to Oracle http://blog.tanelpoder.com/2010/01/15/beyond-oracle-wait-interface-part-2/comment-page-1/#comment-3826 Blogroll Report 08/01/2009 – 15/01/2010 « Coskan’s Approach to Oracle Fri, 12 Feb 2010 18:59:39 +0000 http://blog.tanelpoder.com/?p=553#comment-3826 [...] 1-How to use v$sesstat when wait interface is not enough? Tanel Poder-Beyond Oracle Wait Interface – Part 2 [...] [...] 1-How to use v$sesstat when wait interface is not enough? Tanel Poder-Beyond Oracle Wait Interface – Part 2 [...]

]]> By: Bind Variable Peeking – execution plan inefficiency | Tanel Poder's blog: Core IT for Geeks and Pros http://blog.tanelpoder.com/2010/01/15/beyond-oracle-wait-interface-part-2/comment-page-1/#comment-3762 Bind Variable Peeking – execution plan inefficiency | Tanel Poder's blog: Core IT for Geeks and Pros Tue, 02 Feb 2010 17:11:40 +0000 http://blog.tanelpoder.com/?p=553#comment-3762 [...] my Beyond Oracle Wait interface article I troubleshooted a test case where an execution plan somehow went “crazy” and started [...] [...] my Beyond Oracle Wait interface article I troubleshooted a test case where an execution plan somehow went “crazy” and started [...]

]]> By: Sam http://blog.tanelpoder.com/2010/01/15/beyond-oracle-wait-interface-part-2/comment-page-1/#comment-3683 Sam Sat, 23 Jan 2010 14:57:23 +0000 http://blog.tanelpoder.com/?p=553#comment-3683 Thanks Tanel, I open my eyes! I have been running to waits/statspack/awr reports to find something when session is consuming resources doing nothing. I could find nothing, your blog explains that! Thanks Tanel, I open my eyes! I have been running to waits/statspack/awr reports to find something when session is consuming resources doing nothing. I could find nothing, your blog explains that!

]]> By: The Oracle Wait Interface Is Useless (sometimes) – part 3a « James Morle's Blog http://blog.tanelpoder.com/2010/01/15/beyond-oracle-wait-interface-part-2/comment-page-1/#comment-3656 The Oracle Wait Interface Is Useless (sometimes) – part 3a « James Morle's Blog Tue, 19 Jan 2010 08:17:27 +0000 http://blog.tanelpoder.com/?p=553#comment-3656 [...] analysis and has written a great tool, snapper, for just this purpose. If you have not already read part two of this series, head over to Tanel’s blog now to catch up before [...] [...] analysis and has written a great tool, snapper, for just this purpose. If you have not already read part two of this series, head over to Tanel’s blog now to catch up before [...]

]]> By: Narendra http://blog.tanelpoder.com/2010/01/15/beyond-oracle-wait-interface-part-2/comment-page-1/#comment-3642 Narendra Sun, 17 Jan 2010 19:11:35 +0000 http://blog.tanelpoder.com/?p=553#comment-3642 Tanel, WOW !!!! I can not stress how much I liked the way you walked us (readers) through an analysis which started with V$ views' contents and how they can be pieced together to arrive at the "root cause". Thanks a zillion! As always, learned something new today. Tanel,

WOW !!!!
I can not stress how much I liked the way you walked us (readers) through an analysis which started with V$ views’ contents and how they can be pieced together to arrive at the “root cause”. Thanks a zillion! As always, learned something new today.

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