I am probably not going to write (much) about SQL trace for a single reason – Cary Millsap has already written a paper so good about this topic, that there’s no point for me to try to repeat it (and my paper wouldn’t probably be as clear as Cary’s).

So, if you want to get the most out of SQL Trace, read Cary’s Mastering Performance with Extended SQL Trace paper:

• http://method-r.com/downloads/cat_view/38-papers-and-articles

The above link directs you to Method-R’s article index, as there’s a lot of other useful stuff to read there.

Wow, now I’m done with my first request – to write something about SQL Trace :-)

• http://www.cernatis.com/index.php/oracle-databases/performancetuning/107-fix-high-qlatch-cache-buffers-chainsq-waits

A common cause for cache buffers chains latch contention is that some blocks are visited and re-visited way too much by a query execution. This usually happens due to nested loops joins or FILTER loops retrieving many rows from their outer (driving) row sources and then visiting the inner row-source again for each row from driving row source. Once you manage to fix your execution plan (perhaps by getting a hash join instead of the loop), then the blocks will not be re-visited so much and the latches will be hammered much less too.

The moral of the story is that if you have latch contention in a modern Oracle database, you don’t need to start tweaking undocumented latching parameters, but reduce the latch usage instead. And Laurent has done a good job with systematically identifying the SQL that needs to be fixed.

Good stuff!

If you don’t know what LatchProfX is, read this:

• http://tech.e2sn.com/oracle/troubleshooting/latch-contention-troubleshooting

• http://tech.e2sn.com/oracle-scripts-and-tools

I have uploaded a .zip file (for Windows) and a .tar.gz file (for Unix/Mac). The scripts are all the same with differences in the CR/LF bytes in the files and the init.sql and i.sql which have some OS specific commands in them.

I also uploaded the latest PerfSheet there where I fixed an annoying bug which complained about some missing reference files when opening the file.

I plan to fix the broken links some time between now and my retirement.

I finally figured out how to convert my screen-recordings to uploadable videos, so that the text wouldn’t get unreadable and blurry.

So, here’s the first video, about a tool called MOATS, which we have built together with fellow OakTable Network member and a PL/SQL wizard Adrian Billington (of oracle-developer.net).

Here’s the video, it’s under 3 minutes long. Play the video in full screen for best results (and if it’s too slow loading, change it to lower resolution from HD mode):

Check it out and if you like MOATS, you can download it from Adrian’s website site (current version 1.05) and make sure you read the README.txt file in the zip!

• http://www.oracle-developer.net/utilities.php

Also thanks to Randolf Geist for finding and fixing some bugs in our alpha code… Note that MOATS is still kind of beta right now…

P.S. I will post my ORA-4031 and shared pool hacking video real soon now, too! :-)

P.P.S. Have you already figured out how it works?! ;-)

Update: Now you can suggest new features and improvement requests here:

• http://goo.gl/mod/0ANl

I have planned to create such index for years, but never got to it. I probably never will :) So a good way to extract the descriptions of some scripts is this (run the command in the directory where you extracted my scripts to):

Note: the single and double-quotes may get messed up when the browser tries to be smart and replace them with nicer looking characters (which Unix doesn’t recognize then). When copying & pasting this command, make sure that the single & double-quotes are the regular ones Unix shell can accept):

On Tuesday 22nd March I’ll hold two (yes two) Secret Oracle Hacking Sessions – about ORA-04031: unable to allocate x bytes of shared memory errors, cursor management issues and other shared pool related problems (like fragmentation). This event is free for all! You’ll just need to be fast enough to register, both events have 100 attendee limit (due to my GotoWebinar accont limitations).

I am going to run this online event twice, so total 200 people can attend (don’t register for both events, please). One event is in the morning (my time) to cater for APAC/EMEA region and the other session is for EMEA/US/Americas audience.

The content will be the same in both sessions. There will be no slides (you cant fix your shared pool problems with slides!) but there will be demos, scripts, live examples and fun (for the geeks among us anyway – others go and read some slides instead ;-)!

• Note that the live event is over by now, but you can see the recording from my Oracle Troubleshooting TV show :-)

Check the dates & additional info out here:

• http://tech.e2sn.com/oracle-training-seminars

P.S. People who already attended the AOT2 seminars last year – I will schedule the follow-up Q&A sessions in mid-March!

I have uploaded a little script for that – it’s basically looking up all PMON process IDs and then using /proc/PID/exe link to find out where is the oracle binary of a running process located.

You may have to run this as root (as on some Linux versions I get “ls: cannot read symbolic link: Permission denied” error even when running this command as the owner of all Oracle homes (it seems to happen when your users UID and primary GID are different than thet setuid/setgid bits on the oracle binary):

oracle@linux03:~$ sudo ./findhomes.sh
   PID NAME                 ORACLE_HOME
  4421 asm_pmon_+ASM        /u01/app/oracle/product/11.2.0/db_1/
  4545 ora_pmon_demo112     /u01/app/oracle/product/11.2.0/dbhome_1/
  4547 ora_pmon_test112     /u01/app/oracle/product/11.2.0/dbhome_1/

You can use a similar approach on other Unixes too where the executable location or current working directory (CWD) is externalized in the /proc filesystem – or just use pmap to get this info instead.

Following the huge success of my last hacking session, planned while drinking beer at Graham Woods OOW pre-party and delivered from Miracle’s massive Oracle Closed World event in Thirsty Bear (between drinking beers), I’m announcing another hacking session:

What: Using Session Snapper for flexible Oracle Performance Troubleshooting

When: Wednesday 27th Oct 9:00-10:00 AM PDT (US West coast / California time). Check what’s this in your time zone here

Where: Internet! -> Sign up here: http://tech.e2sn.com/secret

You’ll need to register fast and be “there” on time as my current GotoWebinar account only allow 100 attendees to log on… last time over 100 people signed up, but “luckily” less actually showed up, so nobody got left outside!

BTW, I have figured out what went wrong with audio last time and caused my voice in the end of presentation disappear). A program, which I accidentally launched via a keyboard shortcut, grabbed my Mic input to itself, so gotowebinar’s app couldn’t access it anymore.

• People who will attend my Advanced Oracle Troubleshooting online class or the Virtual Conference I’m organizing with Jonathan, Cary and Kerry – you can also log on to make sure that the (gotomeeting) technology works out OK for you.

See you soon!