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Niall Litchfield's picture

UKOUG

A good day today. I was privileged enough to be at the paper selection day for the UKOUG conference in December 2008. For those who don’t know what happens, and perhaps suspect some sort of elite giving themselves presentation slots, here is roughly how it works. 
Firstly a reasonably large group of reviewers from around the world, [...]

Niall Litchfield's picture

hope for the future

So there I was this morning sitting on the tube (UK underground rail system) when a young student got on an sat down beside me. Obviously being both English and a commuter I couldn’t possibly speak to her!, but I did sneak a look at what she was reading. These turned out to be the notes she had made on her course that she was now going over presumably in preparation for exams. The notes this morning were on normal forms, entity relationship and data modelling. 
 
So there we go, a young female student of IT would be pretty good in itself, the fact that she was studying relational theory was the icing on the cake. There is hope ladies and gentlemen, there is hope.  
Niall Litchfield's picture

The 3 step program

Richard Foote updated his blog today with a description of the 3 step process for troubleshooting technical problems with business systems. Briefly his 3 steps are

  1.  Identify an actual problem that needs addressing, one that’s problematic to the business, not one that only exists in some statistic or in one’s imagination
  2.  Determine what’s actually causing the problem as identified in Step 1.
  3.  Address the specific issue as identified in Step 2.

This started as a comment, but grew a bit. I suspect that most of the time the ‘difficulty’ lies in step 1. Identifying a problem that is causing drag on your employers business. This requires at least: 

  1. understanding the business in the first place.
  2. specifying to a high degree of certainty the issue.
  3. quantifying the impact.

IT staff are notoriously bad at 1) and 3) and business staff are notoriously bad at 2) and 3). For example some colleagues of mine went to a meeting with business users of a core system that has historically suffered significant downtime. We identified and made some infrastructure changes that have reduced the downtime by approximately 40 days a year (that’s right this system was running at circa 80% availability).  The system has been running in it’s new configuration at over 99% availability, and helpdesk calls have all but vanished. The meeting was quite difficult since the business users wanted to complain about the stability of the system. In particular they were upset with the 99% availability statistics because they felt that the stats did not reflect reality, which was that occasionally data was ‘lost’ or application sessions were apparently hung. The fact that other users could continue to work did not mean that the service was available.

ddelmoli's picture

More WAF please…

I’ll get to the point in a minute…  If you’ve spent any time “working” on setting up a home theater in your home, you’ve come across the WAF acronym in many of forums — it stands for Wife Acceptance Factor — and it is a cautionary tale of making sure you keep your setup easy enough so that you don’t end your marriage over your wife’s inability to enjoy Desperate Housewives because she doesn’t like programming the remote :-)

Back before HDTV and satellite TV it was pretty simple here in the US to set up and watch TV.  Generally there was only 1 cable involved (2 if you count the power cable).  If you bought a cable-ready TV you simply connected the cable from the cable company (RG6 coaxial, which carried both audio and video) into your TV and you were in business.  Moving TVs around your house was pretty simple too.  Oh, maybe you had a converter box to watch some pay channels, but for the most part you were good to go — with maybe 50-75 channels in the larger markets.

Things are getting a bit easier lately, but we’ve had a run of complication which I think has seriously slowed the adoption of HDTV and quality sound — the split of audio and video cables — the larger number of cable choices audio-only (optical, coax, patch); video-only (patch, coax, dvi) and mixed (hdmi) along with wonderful new things to learn about like HDCP and DRM.  None of which has made it any easier to make a TV have a good WAF anymore — let alone move them around your house.

The reason I bring this up is due to the shear number of software offers I’ve been getting lately for products that don’t seem to have a compelling ability to simplify things for me or my customers.  They claim to be “better” at some esoteric task, but at the cost of introducing another specialized skill requirement into my customer’s infrastructure.

I got into an interesting discussion with a virtualization consultant the other day who responded to a customer’s concern about the I/O performance of a database on VMWare by installing Virtuozzo for a special system.  I asked why they did that instead of looking to tune the database I/O or maybe scaling up the VMWare hardware or (gasp!) running the database on a dedicated server.  He replied that he recommended Virtuozzo because they wanted everything virtualized and that they didn’t have budget for tuning or new hardware.

Heck, I like Virtuozzo as a virtualization solution and even I thought this solution was all kinds of crazy.

Why add to the customers’ complexity by introducing yet another virtualization technology instead of helping them reduce complexity while still meeting their needs?  The only beneficiary to this appears to be the consultant who can charge fees to maintain this specialized system.  Or maybe the new employee they had to hire to learn and handle this special system.

Personally I got even more upset when I heard that the customer was a public school system — like a public school system needs internal IT complexity instead of simple, reliable systems that do the best job for them.

One-off’s like this are always a challenge — make sure you have a process by which you approve, manage and judge such efforts — understand when one-offs become your new direction, or when they need to be brought back into the fold.

So, there’s two posts, guess I’m on the blogging bandwagon…

As the subject says, there’s my first two real posts, so, I guess I’m blogging.  I won’t guarantee how active I’ll be here, or how much of what I write will be Oracle, as opposed to other stuff, but, for what it’s worth, here I am.

11g is more deadlock sensitive than 10g?

I ran into a situation over the weekend, where an application and schema, which were stable under 10.2.0.3, started hitting ORA-00060 deadlocks in 11.1.0.6, in spite of the fact that no application code changes had occurred.  It seems that 11g was more sensitive to deadlocks in this situation than 10gR2 was.

Bit of a stumper….

Well, I finally decided I have something noteworthy to blog about.  This was a bit of a stumper, that we ran into the other day….I did finally get to the bottom of it, and I thought it worth a mention, here.

We have a three node RAC running 10.2.0.3 on DL-585s.

Hello world!

Just getting started here at WordPress.com.  Soon this blog will be filled with my insights into the Oracle database.

ddelmoli's picture

The Rule of 5

During my 2006 Hotsos presentation I mentioned 2 “rules of 5″ that I like to use — I didn’t come up with them myself, but I’m pleasantly surprised when I find evidence to support them.  Of course, the human brain always finds evidence to support it’s own prejudiced hypotheses (for an excellent read that demonstrates this concept, try Focault’s Pendulum by Umberto Eco).  Anyway, the 2 rules of 5 are:

  1. Most people have 5 times as much hardware as they need (Tom Kyte)
  2. A useful tuning goal for SQL is 5 LIOs per row per row source (Cary Millsap)

Of course, you need to know what LIOs are — a depressingly larger and larger number of DBAs I meet don’t have the foggiest notion of them.

I point you at an excellent blog post by Shakir Sadikali at the Pythian Group which shows off a ten-node RAC cluster brought to its knees by unindexed foreign keys (doh!).  Fixing that and other tuning operations has allowed them to reduce the cluster down from 10 nodes to 2 nodes (or, 1/5th their original hardware).  Score one for #1!

BTW, most people argue #2 by talking to me about aggregates.  My standard response is that any aggregate that is queried heavily is an opportunity for derivation, pre-calculation or optimization.

ddelmoli's picture

2008 Hotsos Conference Material

I’ve uploaded my presentation and the DDL code generation scripts I referenced in my talk.  Just scroll down on the right hand side of this blog to the section marked “Content”.

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