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Welcome to the Wider Layout April 2, 2010

Posted by mwidlake in Blogging.

Noticed anything new about my blog? It seems to have been eating pies and grown wider, somewhat like it’s author.

I’d really appreciate any feedback on if this new width is acceptable or is too large for how you browse the internet. I know it will be too wide for netbook users (of which I am one) without scaling the screen to 75%, but I seriously needed more space.

I very much liked the look of my blog when I set it up and I’ve been very happy with the service WordPress supplies for free for my blog. Their technical support have even answered a couple of questions I have thrown their way over the last 10 months or so {I get better free support off WordPress than I have had from software I’ve paid for}. But the narrow window for the text of my blog has been annoying me since the second or third week after I started. As for code and Explain Plan layout, boy that has been a pain. The use of “sourcode” was an early and much appreciated find and this formatting tool has been improved several times, even in the last 12 months. In fact, that earlier post I just linked to does not fully make sense now as one failed attempt to use the “sourcode” layout now works.

But the width limitation of the style sheet I chose forces me to spend a long time trying to edit code and especially Explain Plan outputs such that it lays out in a readable format. It makes doing technical blogs even more time-consuming.

It all came to a head a month ago when I started using screen shots in my blog. They are rendered down to an illegible 460 pixels wide. This was a real blow as, along with the other threads I want to blog about, I want to do some stuff on AWR in OEM and that can only be done with screenshots.

As you can see, this width issue is no longer such a problem for me. WordPress let you alter the CSS of your style sheet for a fee. But WordPress being the nice chaps they are, you can try it out for free first, to ensure you can do what you want to do. So I got a friend who understands all this web/CSS/html stuff to help me and within a couple of hours we had it sorted. The final step was to give 15 dollars a year to WordPress {I see it as buying them a couple of pints} and I can now bring to you the Wider Widlake Ramblings.

If you are curious as to how this change in width aids layout, see this post I have edited to show before and after layouts.

Screenshots are still going to be an issue, I can’t go beyond 800 pixels for the text window as with the side-bar, window margins, scroll bar etc, the blog would become wider than 1200 pixels (and I decided that 1200 pixels was as far as I could go without it becoming a major problem for some people to read my blog). But code layout is now fine and I can manage screenshots if I am careful.

It pains me to say this, but bigger is sometimes better.


Friday Philosophy – I killed a presentation April 1, 2010

Posted by mwidlake in Friday Philosophy, performance, statistics.
Tags: , , ,

Well, this week saw the latest Management and Infrastructure SIG. I won’t go into the SIG meeting itself just now, maybe later this weekend. If you want an opinion on it, you might like to see what Graham Oaks said.

Being Chair of the SIG I have to find presenters. Being also one of those rare people who enjoys presenting, I know I can always tap one person to present. Me. {If only I could sing, play an instrument, act, do impression, put both my ankles behind my ears(*) or anything that was of any general interest, getting an audience would be so much easier}.

I decided to tackle a topic I have tried before and which I previously did a very poor show of: “General principles on gathering database statistics”.
It is not a title to strike joy into the soul, I know, but it is really important to getting good and reliable performance out of any modern Oracle database. Even other Oracle DBA types tend to find the topic worthy but boring, but I seem to have been forced to know a lot about it and I’ve become sadly very passionate about it.

So, I tried again. I mean, how long should it take to describe the issues with database statistics and the general principles to gathering them? I took my old presentation and stripped out all code, all SQL syntax, all listing of tables and got it down to describing the process. Then I started adding the bits and pieces you need to know to get this half-right. 132 slides. Hmmmm

I tried again and took it higher level. 48 slides. I can do 48 slides in something between 45 minutes and an hour. I was ready.

I had the last presentation slot of the day. I figure if I am going to foist myself on the audience, they should have the right to leave before I start, without missing any of the good stuff. I had 3/4 of the day’s attendees still with me when I started.

I think I killed my audience. Actually, I know I killed my audience. I lost a few as the slot progressed {I kidded myself they had to get back to the office/catch a train} and I made the fatal mistake of not shutting up when I had done 45 minutes. You see, there was all this important stuff I had not mentioned yet! Thankfully, I had a friend in the second row and when I saw him lose the will to live, I stopped. I’d been at it for 70 minutes. What we really needed was the Chair to shut me up but I was the chair.

Anyway, I came away from the talk with two realisations.

  • The topic of gathering database statistics is too large to cover in one presentation session.
  • It really is very boring, even when you are passionate about it.

I think I have no choice but to make this a blog thread (as I threatened to do so about 1 month ago). But I have also promised myself to finish off SQL Audit before I start a new thread and that was 3 months ago.

So I think I am going to have to put some time into this blogging lark. It’s OK though, I seem to go on about database statistics so much that even my cat is staring to avoid me. I’ll just stop watching Star Trek and drinking wine in the evenings and switch to preparing technical blogs. And drinking wine of course.

(*) Up until 2007 I could do this. I get out more now. Despite the stats fixation

Richard Foote on the Impact of stats staying the same. February 16, 2010

Posted by mwidlake in performance.
Tags: , ,
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I just wanted to highlight this very good posting by Richard Foote. He is talking about how SQL execution plans can change when “nothing else does”. Not the table structures, not the code, note the initialisation parameters, not even the table and index stats.

But something does change, which is what day it is (or what hour it is or what week it is). Time moves on and our data does too. If the statistics on the tables does NOT move on, then the CBO thinks that the range of data in the table does not change. So, the CBO thinks your queries are getting further and further “out of range” and so would expect to find less and less data in the tables to bring back. That will lead to plan changes.

If you have noticed my preoccupation with identifying the contents of histograms and high/low values in column stats, you may appreciate that this topic is one I have been finding is a large part of my day job.

Richard explains the point very well, as always, so go have a look.

Friday Philosophy – Are short Posts Better Than Long Ones? February 12, 2010

Posted by mwidlake in Friday Philosophy.
Tags: ,


New Year, same old rambling thoughts January 5, 2010

Posted by mwidlake in Blogging, Perceptions.
Tags: ,

It’s not Friday but, heck, it’s a New Year, there are many of us who might appreciate a non-techie, pointless ramble at the start of the first full working week of a new decade…A Friday Philospohy for the New Year. {If anyone wants to point out the New Decade starts on 1st Jan 2011, go take a running jump – popular opinion is against you, even if logic is for you}.

I found the UKOUG techie conference this year particularly interesting as it was the first major meeting I have been to since I started blogging, and I came across two main opinions about my attempts:

Those who like my blog as it is “chatty” and rambles a bit.
Those who dislike it – because it is “chatty” and rambles a bit…
{oh, and the third opinion, the most common, of utter ignorance of my blog – there goes the ego}.

Well, you can’t please everyone. I was a little saddened, however, as I spoke to a couple of people I really admire in the Oracle Knowledge world and they landed on the “chatty and rambling – bad” side of things. Damn. But they are so good at what they do, I forgive them. The swines.

But then I remembered what I said to a fellow blogger the other month. We bloggers/twitterers all put forward what we blog about in our own style. We might not blog something that is new, we might blog something that is “well known”, but we put it in our own style. Some like it, some do not. It matters not, so long as it adds to the sum of decent knowledge out there.
Some will hate our style and not read, some will read and enjoy. So long as the information gets out there to more people, that is fine.

So, do I think everything I blog is decent knowledge? Oh, I wish. I like to think it is mostly there {and I wish it was all correct} but I am realistic. I test most of what I blog, or I have lived for real most of what I blog, but I will make mistakes. And sometimes I will hit the edge of something good and I put it up there in the hope others will contribute {like the recent one one translating min-max column values into human readable stuff}. And often people do contribute and that is really, really good.

But I do and will continue to make mistakes, be daft, or just put things poorly. I have learned a fair bit in the last 8 months about written communication, the art of communicating to a global audience and also about how not to spread a topic over several weeks as you hope you can “just finish of those half-written blogs in an hour or two” and find it takes weeks. If anyone wants to give me any constructive criticism, please do, but maybe use my email (mwidlake@btinternet.com) rather than flame my postings.

And my last rambling thought for the start of 2010? I am probably going to post less in the next 6 months. I am always sad when the blog by someone I enjoy goes very quiet, but then we all have real jobs to do, so I try to be patient. In my own case, I have noticed I now read a lot less of other people’s blogs as writing my own takes so long. And I am missing too much. There are blogs I really admire or I have discovered in the last 6 months (sometimes both) that I simply fail to really read and they know stuff. So I need to read them. I am going to try and maintain a steady 2-3 blog entries a week, but for the next 6 months I am going to concentrate on learning. Something blogging has taught me is I am really quite ignorant ūüôā

Good wishes for 2010 to all and everyone who stumbles across my ramblings.

The Evenings are Drawing Out December 14, 2009

Posted by mwidlake in Perceptions.
Tags: ,

When do the evenings start drawing out? This year, 2017, it is December 12th. On that day sunset will be 15:51 and about 30 seconds in London. On the 13th it will be a few seconds later . By the 17th of December, the sun will resolutely stay in the sky until 15:52 {and a few seconds}. The days will be drawing out at last. {the exact times will be different for other cities and countries but the DATE will be the same – see the links at the bottom of this page to check for your town and country}

English Sunset by Angie Tianshi

But it is not the shortest day of the year {I should say daytime really, all “clock” days are the same length based on the time it takes for the earth to spin once in relation to the galactic centre.}

What is the shortest day, I hear you all cry?

This year, 2017:

The shortest day is December 21st

The date with the shortest period of daylight {in the Northern hemisphere} is the 21st or 22nd December, depending on how long ago the last leap-year was. This year, 2017,  is one year past the last leap year! Thus is is the 21st. And everyone knows that the the shortest day will also be the day where the sun sets earliest, it makes sense.

Except it does not quite work like that.

We probably all remember from our school days that the earth goes around the sun at an angle from the “vertical”, if vertical is taken as at 90 degrees to the circle the planet takes as it spins around the sun. Think of it like an old man sitting in a rocking chair. He is rocked back in his chair, head pointing back away from the sun in the Northern Hemisphere’s winter and feet pointing slightly towards the sun. Come Midsummers day, around June 24th he has rocked forward, head pointing towards the sun for the Northern Hemisphere summer. One rocking motion takes a year. That rocking motion gives us all summer and winter.

The other complication is that the earth does not go around the sun in a perfect circle. You might remember from diagrams of comets at school that they circle the sun in a big “egg” shape, sweeping in towards the sun, swinging around close to it and then looping out into the solar system before coming back around and in. Well, Earth and all the planets do the same thing slightly. We are actually closest to the sun during the Northern Hemisphere¬†winter – the day we are closest this winter will be Jan 4th 2017 at 14:18 GMT.. It is interesting that most people who live in the Northern Hemisphere just assume we are furthest from the sun’s warmth in our winter. Well, we are closest. We are furthest around the good ‘ol 4th July (in 2017 it will actually be July 3rd).


A result of being closer to the sun is that we are moving through our orbit around the sun slightly faster – when in orbit, the closer you are to what you are orbiting the quicker you move. Our day length is made up of the time it takes the earth to spin ¬†and also about 1/365th of a day – as we in effect spin one extra time in relation to the sun by going around the sun each year. That is why I said the earth spins at the same rate every day when compared to a more “fixed” point of reference like the galactic centre. It takes about 23 hours, 56 minutes and 4 seconds for the earth to actually spin once. The extra 3 minutes and 5-ish seconds is taken orbiting around the sun a bit and that time varies depending how fast we are orbiting.

Thus at closest approach (our winter here in the UK) solar noon {sun at highest point} to solar noon is less than 24 hours and in our summer it is slightly more than 24 hours. But we do not change our clocks, that would be too complicated, we just let them stick to 24 hours, the yearly average of the astronmical day. And, as a result, the clock day and the astronomical day are slightly different.

If you think of a day as a white bar on a black string of 24 hours, that white bar gets longer and shorter as we go through summer and winter. But the bar also moves slowly left and right along the string as the year progresses.

The two don’t quite match as, not only is the earth like an old man rocking in his chair, he is also slumped slightly to one side – he is not sitting up straight.

So there you go. Here in the UK this year (2017)

  • The nights start drawing out on the 12th December.
  • The shortest period of daylight is the 21st December.
  • We are actually closest to the sun, despite it being our winter, on the 4th January 2018.

And just some interesting things to remember:

  • A day as measured from noon to noon (sun at it’s highest point) varies by a few minutes over the year but¬†on average is 24 hours.
  • Part of that day length is not the earth spinning but the earth going around the sun – about 4 minutes.
  • Summer and Winter is not due to closeness to the sun but the tilt of the Earth’s axis in relation to the orbit around the sun.
  • Earth is slumped to one side in it’s orbit
  • Even though this is all simple “clockwork” Newtonian mechanics and mathematicians can work it out very accurately, it is not as simple as it seems.

If you take into account the tiny changes made by the moon and other planets (Mars does have a slight influence on our orbit) it gets even more complex, but those differences are tiny tiny tiny in any given year. Over a million years they make a difference though.

The below tables will help you look up sunset, sunrise, day length and all those things.  I include one for the UK and one for Australia. The jolly nice site the links go to allows you to change the location to wherever you are in the world (well, the nearest Capital).

Table of sunrise/sunset times for London

Table of surise/sunset for Sydney, Australia

What has this to do with Oracle, Database Performance and my day job? Nothing much, except to highlight that the obvious is not always correct, just as it is with Databases, IT and in fact science in general.

I’ll finish with a sunset picture from Auz. Ahhhh.

Outback sunset from ospoz.wordpress.com

Friday Philosophy – Who Comes Looking? September 18, 2009

Posted by mwidlake in Blogging.
Tags: ,

I’ve been running this blog for a¬†few months¬†now and I find it interesting to see how people come to it. A handful of people come to it as I tell them I have a blog page, but most people come across it by either:

  • Links from other blogs or web pages.
  • Search engines.

WordPress gives me stats on these for Today and Yesterday and I can check back on the referrers and searches for any given day, going back several months. Most blog sites provide the same features, I thought I would just run through them for those who do not have a blog.

I can tell when I have been mentioned on someone else’s¬†blog, as I usually see a spike in my hits and their web page is at or near the top of the list of referrers. Interestingly, I will sometimes see a burst of hits from an old reference on someone else’s blog or webpage. I think this happens when a third person has referenced the page or person¬†which then referenced me.

Another interesting facet is the impact on my hits if an Oracle Name mentions me. My busiest day occurred when Richard Foote mentioned a posting I did on “Unhelpful Helpful People” and a couple of other well-known Oracle Names also picked up on the thread. It’s a bit like a small-time-actor getting into a scene with a Hollywood Star :-).

The most interesting, though, are the search engine hits.

My favorite search term to lead to my blog so far is “martin widlake unhelpful people”. I really hope that was someone looking for the post I mention above, as opposed to anything else…

As time goes by, the search engine hits are generating a larger and larger slice of my traffic (and the personal mentions less and less ūüôā ). This is going to be partly due to me putting more content on the Blog to be found but also, as I get more hits and links, search engines will give me more prominence. It becomes self-feeding. Search engines find me as I have been visited before, so I get visited again and Search engines see that I have been visited even more and move me up the list…

{This is, of course, how Burleson gets so much traffic, he always references back to himself and his web sites and appears to have several sites that all cross-reference between them, priming the search engine pump (or absolutely flooding it, I suspect)}.

Some of the most common searches that find me are on obscure items I have blogged about. They may not be of such general interest {such as when I blogged about errors with gathering system statistics {{and more to follow on that topic}} } but I guess when someone hits the same issue or topic, I am one of a very few places that has mentioned it. I get a steady trickle of hits for “c_obj#_intcol#” since I blogged about it often being the biggest object in the SYSTEM tablespace. So perhaps to increase my search engine hits I should not blog about mainstream issues but rather really obscure, odd stuff than almost no one is interested in!

Some days I will get several hits by people searching on “Martin Widlake”. I wonder why they are searching on me specifically. Occasionally, it has been just before I am called about a job. Usually not though {so maybe it was about a job –¬†but then they found my blog and decided against it…}.

Some searches that get to my blog are just odd. Yesterday one search that found me was “how to put fingers on keyboard”. Why? I have no idea why a search on that would land on my blog. Maybe I should try it!

Oh, and I suddenly have a favorite search that found me, hot in today, just as I am blogging about the very topic:

“it‚Äôs a crock of cr4p and it stinks”

Now what is that about? Why search on it and why find me?


How Much Knowledge is Enough? June 13, 2009

Posted by mwidlake in Blogging, Perceptions, performance.
Tags: , ,

I’ve had a bee in my bonnet for a good few years now, which is this:

How do you learn enough about something new to be useful when you are working 40, 50, 60 hours a week?

Another bee is how much do you actually need to know to become useful? The bee following that one is if you do not have enough time to investigate something, how do you find the answer? Buzzing up behind is to¬†fully understand how something works, you often need a staggering amount of back knowledge¬†– how do you get it?¬†Oh dear, it’s a hive in my head, not a single bee.

I am of course in this blog¬†mostly thinking about Oracle and in particular Oracle performance. I think that these days it must be really very hard to get going with performance tuning as¬†it has become such a broad topic. I don’t know if you have noticed but nearly all the performance experts are not in their teens. Or twenties.¬†And precious few in their¬†thirties. Forties are pretty much the norm.¬†¬†We {and please excuse my audacity in putting myself in such an august group}¬†¬†have been doing Oracle and performance for many years and have stacked up knowledge and understanding to help us.

For me this issue was thrown into sharp relief about 4 or 5 years ago. I had become a manager and, although I was learning lots of other skills and things, when it came to Oracle Technology I think I was forgetting more than I was learning. Oh, I was learning some new Oracle stuff but it was at a more infrastructure level. The real kick of reality was going to presentations on performance and Oracle internals. At the end of the 90’s I would go along and learn one or two new things but knew 90% of what was said. By the mid 2000’s I would go along and know 50% , the other 50% would be new. Then I went to one talk and found I was scribbling away as I knew precious little of what was being presented. More worryingly, I was struggling with “How does this fit in with what I already know?”. ¬†I just didn’t know enough of the modern stuff.

That was a pivotal moment for me. It had the immediate effect of making me start reading blogs and books and manuals again. It’s not easy to find the time but I soon noticed the benefit. Even if I learnt only a little more one evening a week, I would invariably find that knowledge helping me the very next week or month. I was back on the road to being an expert. {Or so I thought}. Oh, it had a long term effect too. I changed job and went back to the technical, but that is for another day.

But hang on, during my decline I had not stopped being useful. I was still the Oracle performance expert where I worked and could still solve most of the performance issues I came across. It made me realise you do not need to know everything to be useful and you could solve a lot of problems without knowing every little detail of how something works. A good general knowledge of the Oracle environment and a logical approach to problem solving goes a long way.

I actually started to get¬†annoyed by the “attitude” of experts who would bang on and on and on¬†about how you should test everything and prove to¬†yourself that your fix to a problem¬†had fixed itas otherwise it was just being hopeful. I thought to myself “That is fine for you, oh exalted expert, as you¬†have time for all this and don’t have 60 hours of day job¬†to¬†do every week. Give us a break and get real. Most of us have to get the problem solved, move on and¬†get by with imperfect knowledge. Doing all that testing and proving,¬†although nice in a perfect world, is not going to happen”.

Yep, I had an attitude problem :-).¬†I was getting angry at what I now think is just a difference in perception. I’ll come back to that in a moment.

I don’t think I am going to go back on my opinion that for most people in a normal job, there simply is not time to do all the testing and proving and you have to move on, Making do with received knowledge. It just is not an ideal world. However, we need the experts to uncover¬†that knowledge and we need experts who are willing to communicate that knowledge and¬†we need experts we can rely on. I am very, very grateful to the experts I have learned from. ¬†

All the time on blogs, forums and conversations the issue of “how do we know what sources we can trust” regularly comes up. Well, unfortunately I think that if you do not have time to do the¬†testing and learning needed to become an expert yourself, you have to simple chose your experts, accept what they say but remain slightly skeptical about what they say. Everyone makes mistakes after all. I would advise you only accept someone as an expert and rely¬†on their¬†advice if they¬†are willing to demonstrate why they believe what they believe.¬†Everything else is just an unsubstantiated opinion.¬†

But I’ve come to some conclusions about most of the above questions I started with.

  1. If you are judicious in choosing your sources, you can learn more reliably and easily.
  2. Even a little bit of more knowledge helps and it often comes into use very quickly.
  3. The hard part? You have to make that time to learn, sorry.
  4. Although testing and proving is good, life is not perfect. If you did (1) you might get away without it. But don’t blame the expert if you get caught out.

But I’ve not addressed the point about needing all that back knowledge to fully understand how something works. Well, I think there is no short cut on that one. If you want to be an expert you need that background. And you need to be sure about that background.¬†And that is where it all has fallen apart for me. I started a blog!

I already knew you learn a lot by teaching others, I’ve been running training courses on and off for a few years. But in writing a blog that is open to the whole community, I’ve realised I know less than I thought. A lot less.¬†And if I want to be a source of knowledge, an expert, I have to fill a lot of those gaps. So I am going to have to read a lot, test things, makes sure that when I believe I know something I’ve checked into it and, when I fix something, I know why it is fixed¬†{as best I can, that is}¬†. All those things experts tell us we need to do. And that brings me back to my perception issue.¬†

Those who I think of as the best in this field all pretty much give the advice to test and prove. And they have to do this themselves all the time, to make sure what they say is right. And they are the best as what they say is nearly always right. It seems to be excellent advice.

However, I¬†think it is only good advice, as it is advice you can’t always take, because there is too much else to do. I think sometimes experts forget that many people are just too pressured at work to do their own testing, not because they don’t want to test but¬†because you can only live so long without sleeping.¬†

Anyway, I said something foolish about becoming an¬†expert. I better go and check out some other blogs… start reading some manuals… try out a few ideas on my test database.¬† I’ll get back to you on how I’m progressing on that one in about, say, a year or two? All those gaps to fill….

Blogtastic June 7, 2009

Posted by mwidlake in Blogging.

I wonder how many blog entries world-wide have the title “blogtastic” or “blogging about blogs” or something similar.

I’ve been blogging properly for about 3 weeks now. Why did I start? 3 main reasons.

  • I forget stuff {I’m getting to that age} so I thought a blog was as good a place as any to stick stuff where I could find it.
  • I like to teach.¬† I know, it sounds a bit naff, but I honestly like explaining things and teching people stuff. If I was starting out on my career again, I would do more training.
  • Narcisism. There has to be an element of wanting to be noticed in anyone who blogs! I’d like to be a “C” list Oracle Name ūüôā

After a few weeks blogging, what have I learned?

  • I really like it when I get comments. It is less like talking to an empty room.
  • I am talking to an empty room! When I linked back to my blog from Jonathan Lewis’s blog my hits jumped from a half dozen to 80. They are heading back to a half dozen now.
  • Google does not pick up stuff just because it is on a blog. Which is maybe good as think how many spurious hits you would get for 99% of stuff and it is bad as, not only are people missing out on the great stuff I say, more worryinlgy, when I ask Google about some aspect of Oracle I know nothing about, how much great stuff am I missing?
  • It takes a lot of time to do rigorous explanations of oracle facts, which is what I have always demanded from my Oracle sources (and is why I use “-burleson” in my google searches).

I know my blogs are too long, I’ve been told. But then, they are supposed to be for my own benefit and I like to see why I decided what I think I know.

It takes a loooong time to say what you want to say. I’ve put a few basic techie things up and have not touched on my 2 other areas, VLDB and management. It is going to take me a long time to put down things I want to put down. I have a list of , ohhh, maybe 50 things to blog about already.

And last for now? It’s addictive. I want to put down everything now.I want people to find and read my blog now. I want my stats to be high.Why? Narcisism of course ūüôā But also because if I’m going to teach people there has to be people listening.

And really for last. Why do I want to teach? Well, the post on Consistent Gets says it all. When you teach people, you learn. The hardest questions often come from people who know the least about a topic.

Single Table Hash Selects Investigated May 30, 2009

Posted by mwidlake in performance.
Tags: ,

I think I mentioned in an earlier post that Piet de Visser had posted a nice example of the fastest way to select a single row, via a single table hash cluster. Well, I somehow missed his followup until now (I think because he has two blogs and I was checking the other one).

This is the follow up and he once again provides scripts to repeat his tests. What a nice chap. He shows how care in setting up the hash cluster is a good idea.

Here’s looking forward to his next long train trip so he can add to this thread. I might even spot it sooner next time!