Adaptive Plans in Active Session History

Yesterday, during the talk “The Query Optimizer in Oracle Database 12c – What’s New?” at OakTable World UK 2013, an attendee asked me an interesting question that can be summarized as follows: does ASH show the switch of execution plan that takes place for an adaptive plan? Since I didn’t know the answer, here are […]

Oracle ACE Director

Few days ago Oracle accepted my Oracle ACE Director nomination! In this short post I would like to thank the people that actively supported the nomination. Special thanks go to Yury Velikanov. When during the last Oracle OpenWorld in San Francisco he discovered I was not part of the Oracle ACE program, he decided to […]

System Statistics Gathered in Exadata Mode – When Are They Relevant?

The aim of this post isn’t to explain what the “exadata mode” is. Hence, if you don’t know what it is, before continuing reading have a look to this post published on Kerry Osborne’s blog. The only thing I would like to add is that the “exadata mode” is available as of 11.2.0.4 or when […]

The Broken Statistics: "parse count (total)" and "session cursor cache hits"

The values provided by the “parse count (total)” and “session cursor cache hits” statistics are subject to several bugs. And, what’s worse, for years Oracle didn’t care to fix it. This is my impression, at least. Then, when few weeks ago I read in the Oracle Support note 13837105.8 (Bug 13837105 – statistics “parse count […]

Scripts to Download Oracle Database 12c Release 1 Documentation

In the past (here and here) I already shared with you the scripts I used to download the documentation related to Oracle Database. The aim of this short post is to provide the scripts I just wrote for the latest version: 12c Release 1. download121.cmd download121.sh Happy download as well as happy reading! PS: it […]

Named Notation and SEM_MATCH Table Function

This is a short post about a strange behavior I discovered today… The fact is that it is not really possible to use the named notation with the SEM_MATCH table function. In fact, even though the parameter’s names can be specified, the order of the parameters overrides the specification done with the named notation!?! Here […]

ITL Deadlocks (script)

A reader of this blog, VijayS, asked me to share the script I use to demo ITL deadlocks that I mentioned in this comment. Since other readers might be interested, here is the script. SET TERMOUT ON FEEDBACK ON VERIFY OFF SCAN ON ECHO ON @connect SELECT * FROM v$version WHERE rownum = 1; REM […]

Premature Optimization

Premature optimization, (probably) because of Donald Knuth’s famous line “premature optimization is the root of all evil,” (see Structured Programming with go to Statements) is, at the very least, a controversial topic. The misconception based on that particular quote is that a programmer, while writing code, should ignore optimization altogether. In my opinion this is […]

Ad: CBO Days 2012 – Final Agenda

The 11th and 12th of December and, therefore, the CBO Days in Zurich are approaching. Given the high quality of the speakers that accepted my invitation and the number of people that decided to attend the event, in my opinion it will be a blast! By the way, if you are interested in attending the […]

Does the Parse Time Increase Linearly with the Number Of Child Cursors?

In the last post I discussed a test case generating lot of child cursors. Today I wanted to show you, for the very same test case, that in 11.2 the parse time might increases linearly with the number of child cursors per parent cursor. This is the expected behavior. In fact, to check whether an […]