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How NOT to present November 30, 2010

Posted by mwidlake in Meeting notes.
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I’m at the UKOUOG this week and, as ever, the presentations vary in quality. Most are excellent {or even better than that}, some are not. I was in one first thing this morning and, I have to say, it was rushed, garbled, unclear and there was a definite air of unease and panic. I’m not even sure the guy got to his big point and I could think of at least three major things he did not mention at all.

I think his main problem was just starting off in a rush and never settling down. You see, I was stuck on the top floor of my Hotel and had to run to the venue. Yes, the poor presentation was by me :-(.

I usually present well {modesty forbids me from saying I am a very good presenter – but modesty can take a hike, my ego knows I am capable of giving great presentations}. I am one of those lucky people for whom presenting has never been particularly frightening and, in fact, I find it easier to present to a group of people than talk with them.

But not today. I was already worried about the session, have been for weeks, as I was doing interactive demos. But last night I ran through it, wrote down the names of the scripts and the slide numbers so I could just bang through them and timed it all. 50 mins, I would skip one unneeded section. Calm. I got a reasonable night’s sleep, got up early and ran through it all one more time, making sure my Big Point demo worked. And it did. Yes.

Went down to breakfast, had breakfast and back to the room to pick up my stuff. And realised I was late. Less than 10 minutes to do the 5 minutes over to the venue. So I fled the room, stuffing my laptop in my bag. But not my notes. Or my conference pass. I did not think of this as I stood on the top floor of the hotel, I just thought “where are the lifts?”. They were all below me, ferrying hungry people to and from breakfast. After what seemed like an hour and was only 4 or 5 minutes I decided 16 flights of stairs was OK to go down and, to give me credit, I managed those stairs and the few hundred yards to the venue in pretty good time. I did pause for a few seconds at floor 7, I think, when I remembered my notes. Too late.

But I was now panicked and arrived as a dash. I had to mess about with the Audio Visual guy to get going and started 2 mins past my slot start – and then did the 5 minutes of non-relevant stuff I had decided to drop. It was game over from there, I was failing to find the correct scripts, I was skipping relevant sections and I was blathering instead of just taking a few seconds to calm down and concentrate.

Oh well, my first time in a large room at the UKOUG and I messed up. At least I had the key lesson drummed into me. TURN UP EARLY!!!!

Advert – UKOUG conference, end of November October 30, 2010

Posted by mwidlake in Meeting notes.
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The best Oracle event in the calendar (in my opinion) is only a month away now. From Monday 30th November to Wednesday 1st December the UK Oracle User group Technical and E-Business Suite (TEBS) conference is running. {Being old-school I still think of it as the UKOUG conference but the user group also run other conferences for eg Siebel, Peoplesoft and the up-coming JD Edwards event, dedicated to those segments of the constantly growing world of Oracle}.

I love the TEBS conference. I loved it when I knew almost nobody else attending it because of the breadth and quality of the technical presentations. When I was a manager I liked the fact I could mix going to the technical stuff to going around the demo booths and seeing if any of the services on offer were of interest. And now that I know more people who attend the event, I love catching up with them and also meeting new people who maybe I only knew before by name or reputation.

The social events around the conference are no where near in the same league as those at Oracle Open World – which means that the UKOUG ones are not massive and unfeeling, but of a size where you can bump into friends and be introduced to other people. {And, I should add, the UKOUG staff do an excellent job of organising them}. I’d say half the people I know in the Oracle world I met at the conference.

So having said how much I like the conference, the question is, am I presenting this year? There seems to be an inverse relationship to the number of years I have been attending and the number of talks I do. Back in 2004 I did 3, in 2005 and 06 it was 2, 2007 was 1. 2008 I had to skip the event and last year all my proposed talks were rejected. I blame the fact that the quality and number of abstracts submitted goes up each year.

The good news (or bad news, depending on your opinion) is that I am presenting again this year, first thing on Tuesday at 08:45

My SQL is suddenly performing badly and nothing has changed. Why?

I’m actually very nervous about this presentation as I want to not only describe why SQL might change how well it performs but also demonstrate the reasons – and how you detect them. Demonstrations take an age to prepare and, as fellow presenters know, have this nasty habit of dying under your feet. I’ve not got a lot of spare time at present so I already feel I am behind schedule!

I’ll also be curious how many people from the MySQL field drift into the room thinking it is part of the MySQL stream {which runs on the Wednesday}. Sadly the talk will be of no use at all to them as it is very specific to Oracle!

Despite the presenting duties, I’m really looking forward to the event. I’d love to meet anyone who reads my blog, whether you like it or not. Just stop me and say “hi” if you see me around.

Advert – MI SIG on 5th October September 13, 2010

Posted by mwidlake in Meeting notes.
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The next UK Oracle User Group (UKOUG) Management and Infrastructure SIG is coming up in a few weeks – 5th October in the Oracle City Office. You can find the latest agenda here. If you do not know what we (the MI SIG) cover, it is basically technical topics at a slightly broader level. So not so much example code but how feature X works or how to use Y over 100 databases plus. We also touch on management issues, which I always worry will put some potential attendees of,f but in fact nearly always goes down very well.

We have an excellent line up of topics and presenters for this meeting. Does Exadata work in the real world? Peter Scott will be presenting some of what he has learned doing this. Want to know about oracle’s latest licensing options and how to save money? Alex Sandercock from Turnstone Services will be talking about that. Confused about how storage is changing and how the database interacts with it? James Moorle will cover that one.

It has been a real struggle getting the agenda together for this meeting, I can’t believe we have ended up with such a strong one in the end. I mean, I am not even having to bore everyone with my voice again.

The first problem was I just failed to get the organising started. As the Chair, it is my main function to sort out the meetings. It was always “tomorrow” as I had so much on for every “today”.

The second problem was we were up against Oracle Open World. We had a few people “in hand” who had indicated they would be happy to do a talk for us, but were scheduled to do OOW. I thought it was a bit mean to turn us down for some obscure vendor event in the US. So we moved our event by a month.

The final problem was that we still had trouble with speaker availability, as it was now so close (it might not seem close if you are considering going to a meeting, but if you are being asked to sign up to preparing and giving a presentation, 5 weeks is not a lot of notice).

It all came together in the end, with the help of the co-chairs, especially Neil Chandler.

I know I have said this before, but I struggle to understand why SIG meetings are not flooded with people coming to them. It is free training in effect (if your organisation is a member of the UKOUG – £80 otherwise, I think). All the presenters are experts, often presenting similar talks to those given at Oracle Open World or the UKOUG Conference. OK, it is a day not working in the office but as well as the “free training” you meet up with other people who have similar work issues as you. I find it invaluable to have a circle of external people I can occasionally say “What do you think of this” to. The meeting other people is aided by us retiring to a pub after the event, for those inclined to do so.

I try to get to SIGs when I can and in fact, if I was not at my own on the 5th, I’d like to be at the modelling and architecture one – I’ve been meaning to get to that one for ages.

Friday Philosophy – The Science of Oracle June 11, 2010

Posted by mwidlake in Friday Philosophy, Meeting notes.
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3 comments

The title to this blog is very misleading. It is not about scientifically understanding how Oracle technologies work or even about the technology itself.

It is actually about the fact that a lot of scientific organisations, both academic and commercial, work with Oracle technology in ways to do directly with the science {as opposed to using it for CRM, HR or tracking students and results, which they also do but I’m not interested in that}.

If you have worked in Academia or charitable scientific organisations it can be a little suprising that Oracle is used so much, as it is expensive and corporate – there is a tendency to be poor and anti-corporate in such environments. But the thing is, Oracle is able to handle large amounts of complex data, in many formats, in many ways, and most programming languages can easily access the data in the database. You can achieve a lot with just PL/SQL and Java of course.

Commercial scientific organisations, like large Pharmaceuticals, use it for the same reasons of course, but for them the cost is not such an issues {I can imagine IT managers in such organisations going “It damn well IS an issue!” but trust me, not in the same critical way}.

What is the point of this blog? Well, it’s about user communities. The scientific community have a tendency to push the Oracle database further than most Oracle users do. Take data volumes. I worked for many years for the UK-side of the Human Genome Project and part of what I did was create an Oracle database that scaled to 100TB. Even now that is pretty large but I was designing and implementing it back in 2004-2005. The data volumes CERN are going to have to handle for the Large Hadron Collider just dwarf that, and they only hold summarised data of summaries of the actual raw scientific data generated.

Another aspect is coping with very rapid change, for example systems to support lab processes. This is similar to your standard factory management system except that the level of change can be daunting. The process can change, well, weekly, as the science and techniques improve in the lab. Those scientist might even completely change what they are doing when some unexpected avenue opens up. I say “might”, seemed to happen every month.

In scientific organisations there tends to be more openness about what and how they do things. Academic and charitable scientific organisations tend to put less barriers in the way of exchanging knowledge than corporations do and so that encourages more exchange of information. When I was working in the area I was positively encouraged to go to conferences and present. Obviously this is not always true and scientific corporations, like Pharmaceuticals, have gained {rightly or wrongly} a reputation for being very reticent about sharing any knowledge at all. But often the individuals involved will share.

So, the scientific community push areas of the technology very hard, they tend to be an open bunch of people, cost is often critical and, the final thing I have not mentioned, is that they often speak a language only vaguely recognisable as English, due to the jargon. Sounds like a community to me.

The real reason I mention all this is that it looks like, after about 4 years of considering and discussing having a science SIG {Special Interest Group} in the UKOUG, I will finally be putting together an agenda for an initial meeting for such a thing. I wonder if it will be a success?

Northern Server Technology Day – Advert April 22, 2010

Posted by mwidlake in Meeting notes.
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I’m a bit late doing this, but next week is the UKOUG Northern Server Technology Day.
As the title suggests, this is a day of technical presentations for Oracle users in the North of England. Of course, it is open to any UKOUG member (and anyone else, for a small fee), but the idea behind it is to provide a user group event for those who are not based in the South of England and so might struggle to the usual events. This year the day is being held in Leeds, which is where I was at college, so I am more than happy to return to my old stomping ground and support the day with a presentation on Database Statistics.

There are other, probably much better, presentations by David Kurtz, John Hallas, John Scott, Piet de Visser and David Phizacklea too. I’ve seen them all do their stuff before and it should be a cracking day. Check out the agenda via the link at the top of this post.

If you are an Oracle user who is based up in the North and have an interest in the meeting, I would urge you to make the extra effort to attend. It is a constant complaint that the UKOUG is biased towards having events in Reading, London and the Midlands and not a lot elsewhere, but to have events further afield there needs to be an active and interested audience to justify the event. The better the event is supported, the more likely it is to continue and prosper and potentially attract other UKOUG SIG meetings North.

Actually, on that note, I will also mention the Scotland 2010 conference meeting, a must for Oracle users in Scotland or those who would like to mix a technical conference with visiting Scotland {and I have to say, I do enjoy visiting Scotland}. Not sure yet if I can get there myself this year :-(

Advert for the Management and Infrastructure SIG March 24, 2010

Posted by mwidlake in Management, Meeting notes.
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I’m a bit late doing this (life is just too busy at the moment) but I want to mention the next Management and Infrastructure Special Interest Group meeting of the UKOUG next Week. Tuesday 30th, being held in Oracle’s London City office.

I get asked by people what exactly the MI SIG is? {Honest, I do, I got asked twice this month alone!}. Is it a management meeting or is it another one of the technical SIGs, like the UNIX, RDBMS and RAC/HA SIGs? I’ve struggled to come up with a single line to sum it up. Other than to say “Both”.

It might be easier to sum up the target audience. The MI SIG is for technical people who need to deal with Oracle as a component of a large IT environment. Most of the audience could knock up a PL/SQL script to create a new set of tablespaces each month, would be able to instal Oracle {if given a couple of days and the manuals to peek at} and could explain two-phase commit. Maybe.
But what they have to deal with in their working lives are things like using Grid Control to manage 500 instances, understand what options are there for providing disaster recovery {if not the exact commands to eg set up physical standby or active/passive RAC}, knowing enough about storage options to make a sensible decision on which is best for each type of Oracle system they have. So it is a technical SIG, but covering general principles and, well, Infrastructure.

And the Management? Well, when the SIG started this bit was really interesting to me. When you have a lot of IT going on, especially in large organisations, the people looking after Oracle are not the people looking after Networks, or Storage, or Backups or half a dozen other things. And you probably have a team of people doing all that Oracle stuff with/for you. So you have to hire staff and keep ‘em happy and deal with teams who you have no power over but you need them to do stuff for you. And that Management part can be a lot harder than the technology, especially if you never planned on being a manager but just woke up one day with that monkey on your back.

So with the technical aspects of Large IT Infrastructure comes the management component too. The SIG is there for that audience.

I chair this SIG, so I am more than a little bit biased, but I think it is a good line-up of talks for this up-coming meeting. We have two talks on using OEM/Grid Control, one around using it for deploying clusters, one about how you go about integrating it with the likes of LDAP, Kerbros and using the Custom Metrics, ie plugging it into the wider infrastructure.

We also have a presentation on the latest/greatest Exadata2, from some Oracle friends.

To wrap up the technical talks I am going to try and explain some of the guiding principles for gathering statistics for you oracle databases. Not the details of DBMS_STATS command syntax, but why you need good stats, how you get them and the issues we all seem to end up facing with it.

Balancing the techical side is a talk on Birkman and understanding teams and people.

So, you can see it is a line-up matching the diversity of the SIG’s purpose.

As I said earlier, I initially was very interested in the management side of the SIG and I worried I would be pretty lonely in that opinion. For various reasons, those of us on the technical side tend not to have much time for those “soft skills” we associate with management theory. However, when I took over the SIG over a year ago, I asked the audience if they would want some talks on hiring staff, dealing with people, motivation… Over 60% of the audience said “YES!”. Quite loudly. About 30% said “OK, so long as we get technical stuff as well”. 6% said “over my dead body”.

I think the reason so many wanted the management side as well is, whether we like it or have an affinity for it or not, it is part of the job. And so we need to be able to do it. Personally, I quite like the human side of IT, but my wife tells me I am strange.

If your organisation has UKOUG membership it is free to come along to the SIG (one person per membership, excluding Bronze membership) Anyone can come along for £80. You would be very welcome and I am sure you will learn new stuff. Don’t let the fact that we retire to a pub afterwards where the chair buys a round sway your decision to come along at all.

DBMS SIG March 10, 2010

Posted by mwidlake in internals, Meeting notes, performance.
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5 comments

I went to the DBMS SIG today {DBMS Special Interest Group meeting of the UK Oracle User Group}. Don’t worry, I am not going to run through the set of presentations and make comments on them – although I like reading such entries by others on their blogs, I generally like them due to the style of writing as opposed to getting information out of them. But there is the odd tidbit that can be worth disseminating to as wide an audience as possible and I like to do my bit.

Having said I won’t go through all the talks… :-). No, I just want to comment that all the talks had merit at this meeting and, quite rightly, the meeting was full. This is nice to see as last year SIG attendance fell across the board, due to the “economic climate”. Very daft, in my opinion, as I see SIGs as free training plus networking opportunities (sorry to use the “networking” word” plus different viewpoints, all of which are invaluable at any time and especially valuable when things are hard.

Go to SIGs (or whatever is available in your country) as it is always worth the day invested. Where else can you see half a dozen experts give opinions and also corner them and ask them more stuff as well?

Anyway, the tidbits. First, Jonathan Lewis demonstrated how he goes about solving issues with complex SQL statements. It was terribly feindish and extremly clever and needs incredible in-depth knowledge of the oracle RDBMS… He draws a pseudo Entity Relationship Diagram of the tables involved, adds in some figures on what filtering will achieve and what ratio of records will be involved in table joins and asks the question “what will probably happen” a couple of dozen times. Yes, I lied, it does not need vast knowledge. It needs a clear, simple approach to solving the problem. And an ERD. I love ERDs and rue their general demise. I use exactly the same method myself to investigate complex SQL performance issues {I think I could be accused of trying to ride on shirt-tails here, but honestly, the step I take if an Explain Plan does not help me is to ERD the statement and look at the indexes and ratios between tables to see how I , as a human, would solve the query. Chatting to a few other old lags, it is a relatively universal approach by those of us who have used ERDs}. If you are a member of the UKOUG I strongly recommend downloading the slides to Jonathan’s talk. If you are not a member, maybe Jonathan will present it again at another venue, or you could get him to come along and do a course on tuning. {Jonathan, if you get a gig as a result if this, I want a pint of Marston’s Pedigree, OK?}

{And thanks to Sean malloy for commenting to provide a link to a published version of Jonathan’s method – Jonathan did mention this, highlighting the fact that it is his first real foray into SQL*Server. However, the method is database agnostic. This is the article}

Second tidbit. Adrian Dodman and Owen Ireland (who both look remarkably like Hollywood hearthrobs in their pictures, but different as their in-the-flesh selves, though very decent chaps they are too.) did an excellent talk on VLDB physical standbys, a topic that has particular resonance for myself. They mentioned parallel_execution_message_size. This defaults to 2k, on 10g at least. It is a rubbish setting. No, let me not beat about the bush, it is an utterly rubbish setting. If you use parallel query, parallel recovery or parallel anything-at-all, check out this parameter and, due dilligence allowing, increase it. Try 8k as opposed to 2k and even 16k. The manual on it says the default of 2k/4k is fine. It ain’t. Increasing the value just takes some memory out of the shared pool and, these days, if you can’t afford a few extra KB out of your shared pool, you need to replace your server with something costing about twice as much as a top-end desktop PC. { Why am I so vigorous in my opinion on this parameter? Well, I had a situation a few months back of trying to migrate a database to a new geographic location for a client in Germany. We did a backup/recovery type operation to do this. Applying the redo logs was proving to be a performance issue so Oracle Corp suggested parallel redo log application. It ran a LOT slower than single thread, about 300% slower. However, increasing the parallel_execution_message_size from 2k to 8k made the parallel log application about 400% faster than single thread. ie a dozen times faster. I know from presentations by Christian Antognini and discussions with others that it is a key parameter to getting parallel query to perform well too.}

Last tidbit. Don’t drop the OUTLN user. Yes, I know, why would you? Just don’t, OK? Especially on Oracle 11. If you do, for whatever reason, DO NOT SHUT DOWN THE DATABASE. Call Oracle Support and pray. Thanks go to Peter Mahaffey for that one. Yes he did. It all went terribly wrong for him.

Dealing with Bind Issues December 1, 2009

Posted by mwidlake in Meeting notes, performance.
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11 comments

One of the presentations I have seen today was on handling bind values. I can’t say it was, for me, the best I have seen this week, I’ve done a lot of work on binds in the past so I had come across most of the material before. Should I have bothered?

Well, there was one little gem in there which struck me as very simple and potentially very effective.

Bind variables and histograms are not a good mix, as has been commented on many, many times. In essence, if your data in a column is skewed so that some values match very few records and others match a large number, when oracle sees a SQL statement with a bind value being compared to that column, it peeks at the first value being passed in with the bind and uses it to decide on the plan (this is pre 11G, by the way).
That plan is then used for every execution of that sql statement until it is thrown out the SGA. Which is jolly unfortunate if all the values subsequently passed in via the bind do not suit the plan. 

The solutions to this usually boil down to one of three approaches; remove the histograms on the column in question so that all values are treated equally;stop it being a bind/prevent bind peeking; force the “bad” plan out of the SGA and hope the next parse gets a better plan.

All have their merits and drawbacks.

Well, in this presentation there was a fourth solution. Something like this:

if :status in (1,2,3) then
  select /*+ cardinality (t1 100000) */
  from table_1 t1
      , table_t t2
  where t1.status=:status
  and....;
else
  select /*+ cardinality (t1 100) */
  from table_1 t1
      , table_t t2
  where t1.status=:status
  and....;
end;

I might be missing something blindingly obvious here (and this might be a common solution that has just passed me by), but it seems to me to be a simple and effective solution that could be used in many situations.

I also learnt that it is rare not to find at least one good thing out of any presentation, so long as you keep paying attention.

UKOUG So Far December 1, 2009

Posted by mwidlake in Meeting notes.
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It is the start of the second day (actually, an hour in, have a small “one beer too many” issue to cope with so I missed the first session) and so far I’ve very much enjoyed the event.

I saw several good talks yesterday. highlights for me were; Graham Wood’s talk on ASH, Alex Gorbachev on ASM and Doug Burn’s talk on parallel processing. Doug’s talk fell foul of the curse of all talks, the carefully prepared and tested demo deciding not to play, but a few of us clustered around his laptop to see the final results after the event.

I really wanted to get to Randolf Geist’s talk but one of the “problems” with having been coming to the conference for so many years is meeting up with people you have not seen for ages, getting into a conversation and realising that the next set of sessions started 10 minutes ago.

Today my chairing duties start, with Luca Canli from CERN talking about compressing very large data sets, which is something that is highly pertinent to my current work.

Tomorrow I chair 4 sessions:
Larry Carpenter on DataGuard 11GR2. Larry is an old friend, he gave us some excellent support on Dataguard 5 or 6 years ago.
Piet de Visser on Good Indexing. Piet is up against Jonathan Lewis and James Moorle and he has joked to me that it could be just him and me in the room, but I doubt that. I don’t want to discourage anyone from going to see JAmes and Jonathan (both give cracking presentations) but heck, come and see Piet :-)
I’m then chairing Christian Antogini, talking on parallel processing. I’ve never “Met” Christian, I’ve been in a couple of large discussions where he was also there, so I am looking forward to meeting him properly.
My final Chairing duty is right at the end of the last day, when only the die-hards and those who’s train ticket is pre-booked late in the day remain :-)
I’ll be chairing Husnu Sensoy who is talking about backing up enormous database, which many of you will know is a topic close to my heart. That should be a fine rounding off of the conference.

My aim today is to get to a few more sessions and get through the evening without drinking that one beer too many.

UKOUG Conference approaches. November 26, 2009

Posted by mwidlake in Meeting notes.
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Well, it’s that time of year again. It’s dark by 4pm, weather is miserable and I’m already sick to the hind teeth with Christmas, thanks to the never ending drive by the commercial sector to bully me into buying tatt and rubbish “to make christmas special”.

But there is another staple of the season of the end of November/start of December, which is to trek over to Birmingham for the annual UKOUG conference. Except of course that there are now several conferences run by the UK Oracle User Group, for different Oracle sectors and regions, but this is The Technical Conference. Back to three days and focusing on the database, application server/E-business suite and development. Just like the good-old-days before Larry bought up 300 companies and a big chunk of the software business services industry.

I’ve been lucky enough to go to a couple of Oracle Open Worlds (OOW) and mighty impressive the event is. But I prefer the UKOUG annual conference. It’s not the huge (and, I feel, overwhelming) size of OOW, but still pretty big, I think 10 streams of presentations, workshops and panels this year, and has the added bonus of being more Real. The presentations are to a large part independent from Oracle Corp and even the Oracle Corp presentations tend to be a little less Corporate and a little more Real. People say “how it is” at a User Group.

Plus there is more a feeling of meeting friends and colleagues and like-minded practitioners of every-day living and learning with oracle.

For those new to the scene, it’s far more easy to get to grips with than OOW and yet with Big Names doing top technical presentations, spread over a range of levels from introductory to the esoteric details of stuff most of us never need to know. Plus everything in-between.

Since 2003 I have presented every year except last year {when I decide to go play with elephants in Thailand instead}. I’m not presenting this year either and I would be lying if I said I was upset. I’m utterly gutted. But then I saw the spread of talent and interesting topics when I helped score the abstracts back in May and competition this year was fierce. I’ll be chairing a few sessions though and trying to meet up with people I know, and also people I don’t know but would like to.

If you see some small (5 foot sod all) chap with little glasses, short, brown hair and cream trousers, that is probably me. Come over and say “hi”. If you already know me and come over and say “hi” and I look like a rabbit caught in headlights, well you should know me by now and that I am utterly rubbish at recognising faces or remembering names, but that’s OK as I rarely bite and will be happy to apologise for my lack of social skills. If I’m anywhere near a bar, I’ll probably buy you a drink too, but then you have to buy me one. I’ll be under the table first though.

So, if you are also heading to Birmingham, see you there. If you are not, you are missing out on a fantastic Oracle event.

 

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