Visualizing SQL Plan Execution Time With FlameGraphs | Tanel Poder: SQL Performance Tuning, System Troubleshooting and Training
Introduction Brendan Gregg invented and popularized a way to profile & visualize program response time by sampling stack traces and using his FlameGraph concept & tools. This technique is a great way for visualizing metrics in nested hierarchies, what stack-based program execution uses under the hood for invoking and tracking function calls. If you don’t know what FlameGraphs are, I suggest you re
Peeking into Linux kernel-land using /proc filesystem for quick’n’dirty troubleshooting - Tanel Poder Consulting
Peeking into Linux kernel-land using /proc filesystem for quick’n’dirty troubleshooting This blog entry is about modern Linuxes. In other words RHEL6 equivalents with 2.6.3x kernels and not the ancient RHEL5 with 2.6.18 kernel (wtf?!), which is the most common in enterprises unfortunately. And no, I’m not going to use kernel debuggers or SystemTap scripts here, just plain old “cat /proc/PID/xyz” c
An index of my TPT scripts - Tanel Poder Consulting
A lot of people have asked me whether there’s some sort of index or “table of contents” of my TPT scripts (there’s over 1000 in my TPT script repo right now). 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 to just grep for Purpose: in the scripts directory: grep -i Purpose: ash/*.sql awr/*.sq
Advanced Oracle Troubleshooting Guide – Part 10: Index unique scan doing multiblock reads?! - Tanel Poder Consulting
Advanced Oracle Troubleshooting Guide – Part 10: Index unique scan doing multiblock reads?! When you troubleshoot an Oracle (performance) problem you usually want to find out what are the problem sessions doing (wrong) and then why are they doing it. The “what” question is usually answered using some wait interface based method – like ASH or SQL*Trace, which both add plenty of extra details to the
SQL_ID is just a fancy representation of hash value - Tanel Poder Consulting
…Or in other words, how to translate SQL_ID to a hash value :) I once wrote a script to demo this in my Advanced Oracle Troubleshooting class. Check this, I’ll run a query and then check what is its SQL_ID and HASH_VALUE from V$SQL: SQL> select * from dual; D - X SQL> select sql_id, hash_value from v$sql 2 where sql_text = 'select * from dual'; SQL_ID HASH_VALUE ------------- ---------- a5ks9fhw2v
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