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December 2011

Approximate NDV

This is just a temporary note (comments disabled) to make sure that any subscribers get a message that Amit Poddar has given me permission to publish his presentation on the 11g Approximate NDV. There are links to a white paper and the presentation slides on my posting about Hotsos 2009 where I saw him give the presentation.

Note – do not link back to this posting, I intend to delete it in a few days.

The Thing…

The first film I ever saw on VHS was The Thing (originally released 1982). I’m not sure exactly how long after the cinema release it was, but I remember I was still in school, so I guess it was about 1983-84 and I was about 14-15 years old. A kid at school had just got a video recorder and I went over to his house to see it. It was one of those giant top-loader things. I was totally in awe of it. I thought the film was pretty neat too. :)

"Workarounds" for ORA-04091

In the previous post, we demonstrated running into the mutating table error. The example involved the well-known EMP table and a business rule that we are trying to implement: all departments with a Manager should also employ a Clerk. We started our implementation for that rule by writing a straight-forward 'after-row-insert' trigger on the EMP table.

Up the Villa…

I had a bit of good news the other day. Nephew #2 (6 years old) is now playing for Aston Villa Academy. He’s quite small for his age and he trialed with a group of boys a year older than him, so my brother said he looked tiny and the kit they gave him was gigantic on him. He’s used to playing with Nephew #1, who’s just turned 10, so playing with bigger kids doesn’t phase him and he’s a bit more cocky than Nephew #1, which they seem to like at these places. Anyway, at the end of the session they said they want him. They are not allowed to sign exclusively until they are 8 years old, so he can keep playing for Wolverhampton Wanderers Academy and Telford.

So now I have to support:

I wish

Here are a few thoughts on dbms_stats – in particular the procedure gather_index_stats.

The procedure counts the number of used leaf blocks and the number of distinct keys using a count distinct operation, which means you get an expensive aggregation operation when you gather stats on a large index. It would be nice efficiency feature if Oracle changed the code to use the new Approximate NDV mechanism for these counts.

Getting Started with Dtrace

Structure of a dtrace script

#!/usr/sbin/dtrace -s

something_to_trace
/ filters /
{ actions }

Something_else_to_trace
/ filters_optional /
{ take some actions }

The script has sections that fire if the specified probe fires in the OS. For example, if  do a  send over TCP then my “something_to_trace” could be a probe (an event) called “tcp:::send” . I could further filter by receiving machine’s IP address. Then when a packet is sent over TCP and the receiver is the IP in the filter I can take some actions like state the size of the packet.

What can I trace?  What are the possible “something_to_trace”, ie the probes?
To get a list run of OS probes, run

Provision Oracle RDBMS software via RPM

I have always asked myself why Oracle doesn’t package their software as an RPM-surely such a large organisation has the resources to do so!

Well the short answer is they don’t give you an RPM, except for the XE version of the database which prompted me to do it myself. The big problem anyone faces with RPM is that the format doesn’t seem to support files larger than 2GB. Everybody knows that the Oracle database installation is > 2G which requires a little trick on our side. And the trick is not even obscure in any way as I remembered: some time ago I read an interesting article written by Frits Hoogland about cloning Oracle homes. It’s still very relevant and can be found here:

http://fritshoogland.wordpress.com/2010/07/03/cloning-your-oracle-database-software-installation/

Now that gave me the idea:

Mike Carey: The Naming of the Beasts…

“The Naming of the Beasts” is book 5 in the Felix Castor series by Mike Carey. Juliet, the succubus, has gone all wild, beaten up her human wife and is on the verge of feasting on aroused men’s souls again. Felix’s friend Rafi, still possessed by the demon Asmodeus, has gone AWOL and started a killing spree. Life’s never easy when you’re a freelance exorcist… :)

This is the last in the series so far and it maintains the pace of the other books, while tying up a lot of loose ends. According to Wikipedia the next book is out late 2001 (imminently). It will be interesting to see what Felix does next, since the main thrust of the story of the first 5 books is now concluded.

Cheers

Tim…

And so the evenings start drawing out (honest!)

I know I’ve blogged about this before, but it was early on when very few people read my ramblings, so I am mentioning it again…

For those of us in the Northern Hemisphere, today is the day when the evenings start drawing out, which personally I find a relief as going home in the dark depresses me. Sunset tomorrow will be later than today – by all of a few seconds but, heck, later is later. {If I am out by a day, please don’t tell me – don’t shatter my good mood!}

WordPress 3.3 Released…

WordPress 3.3 is now live and ready for download.

The automatic upgrade was as smooth as ever. A couple of themes needed to be upgraded too. The menus are a little different and there is now a new persistent dashboard header, but it all seems like business as usual for the casual blogger like me.

Cheers

Tim…