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February 2012

Hotsos Symposium 2012

It’s almost time for Hotsos’s 10th annual Symposium. This year’s conference will be held March 4 – 8 in Irving, Texas. The Hotsos Symposium is probably the best performance oriented Oracle conferences in the world. I am happy and humbled to be speaking at it again this year as the lineup of speakers is once again world class. It’s great to have several other Enkitec’ies on the bill as well. Both Karen Morton and Tanel Poder will be presenting too. Enkitec is also a sponsor of the event this year, so we’ll be hosting a couple of Exadata focused happy hours as well. There’s still time to register. Hope to see you there.

 

RMOUG Debrief

I’m back home after a very pleasant few days in Denver. As always the RMOUG conference was great fun, the location delightful, and the people were friendly, and the organizers did a great job of looking after the presenters and making things happen. It’s a terrific event – just big enough to have a real buzz, but small enough (I’d guess about 700 – 800 people) that you don’t feel lost in the crowd.

All three of my presentations seemed to go well - one person even started to applaud (which got the whole room going) when I got to the really important slide in the first session.

Jonathan Gennick of Apress had brought 100 copies of Oracle Core and was selling them off at a special event price of USD 20 – and I think he only had one or two copies left by the end of the event; I know that I autographed an easy 40 or 50 copies.

Friday Philosophy – Tosh Talked About Technology

Sometimes I can become slightly annoyed by the silly way the media puts out total tosh and twaddle(*) that over-states the impact or drawbacks about technology (and science ( and especially medicine (and pretty much anything the media decides to talk about)))). Occasionally I get very vexed indeed.

My attention was drawn to some such thing about SSDs (solid State Discs) via a tweet by Gwen Shapira yesterday {I make no statement about her opinion in this in any way, I’m just thanking her for the tweet}. According to Computerworld

SSDs have a ‘bleak’ future, researchers say

Tables and Their Indexes Should be Located on Different Disks – What is Wrong with this Quote?

February 17, 2012 As I mentioned in a previous blog article, I placed an order for the book “Oracle Database 11gR2 Performance Tuning Cookbook“, mostly because I was curious how the book would compare with the “Oracle Database 11g Performance Tuning Recipes” book (my review of that book was a total of about 35 typewritten pages in [...]

Subquery Factoring

When I wrote a note last week about the fixes to the subquery factoring optimizer code in 11.2.0.3, I finished with a comment about having more to say on the test case if I materialized the subquery. Today’s the day to talk about it. As a reminder, here’s the query, but with the /*+ materialize */ hint in place:

with subq as (
	select
	/*+ materialize */
		outer.*
	from
		emp outer
	where
		sal > 1000000
	and	outer.sal > (
			select
				avg(inner.sal)
 			from	emp inner
			where	inner.dept_no = outer.dept_no
		)
	)
select	*
from	subq
;

Here are the three plans – from 10.2.0.5, 11.1.0.7, and 11.2.0.3 respectively:

Dropped Tables, Hiding Extents and Slow DBA_FREE_SPACE Queries

My last post was on slow dictionary queries caused by having many, many thousands of extents in your database. This post is about a special case of this problem, which I encountered recently. It was on an Exadata box – Exadata is not particularly relevant to the issue, but I’m curious to see if mentioning Exadata will make this post more popular :-)

I was querying the used and free space on a very small database on the client’s X2-2 1/4 rack Exadata machine. The query was really slow, taking about 30 seconds. This is a FAST box, what is going on?

I quickly realised that the problem was specific to one tablespace:

RuOUG in Saint Petersburg

On February 10th I was in Saint Petersburg on a seminar organized by Russian Oracle User Group. Actually, it was mostly prepared by company called Devexperts. Seminar took place in their office, with most presentations done by their people.

Product Review

A while ago I said that I’d be posting a product review here. Unfortunately work got in the way of me posting the review as quickly as I would have liked. The nice people at Ucertify sent me a review kit for the OCA Oracle Database 11g: Administration 1 exam. I very much like the […]

Slow querying of DBA_EXTENTS, DBA_FREE_SPACE and dropping tables

Are you finding queries to identify free space, the size of segments or details of extents in your database are very slow? You could have a database with a very, very large number of extents. If you are on version 9 or up, I would suggest you check the extent management settings for any tablespace holding large segments (see later).

{Caveat – I’m writing this posting based on what I remember of some issues I had on two V10.2 databases 2 and 3 years ago respectively, and those systems are no longer available to me. So please treat everything I say here with some caution – I’ve not checked and verified it to the level I normally would. But I wanted to move this information from another posting I am writing on a recent experience I will verify…}

Introducing the Hardline According to Tim Hall…

I’ve made quite a big decision today. I’ve decided that I will no longer waste my time answering crap questions on my forum. I don’t mean I will not answer any questions. Just that I will not answer questions where the poster has put little to no effort into the question. The sort of things that drive me mad are: