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DB Optimizer vs OEM

Oracle OEM is slower, more complicated and it if it breaks, which has plenty, it’s super hard to fix.
OEM has nothing like visual sql tuning diagrams. If OEM can’t tune a query they you are at a dead end street with no way out. With DBO you’ve got the VST diagrams which explain tons about what is going on with the query
There is no load testing or SQL IDE in OEM
OEM’s SQL Tuining Advisor (STA) has a solid history of not being able to tune queries or worse still “tuning” the query and making it run slower

Session Undo

One of the simple scripts I use from time to time monitors the amount of undo generated by a long running session by taking a session id (SID) as an input and joining v$session to v$transaction:

column start_scn format 999,999,999,999

        tr.start_scn, tr.log_io, tr.phy_io, tr.used_ublk, tr.used_urec, recursive
        v$session       se,
        V$transaction   tr
        se.sid = &1
and     tr.ses_addr = se.saddr

---------------- ---------- ---------- ---------- ---------- ---
 136,509,466,121   10730956     358074          1          1 NO
 136,515,115,543         12          0          1          3 YES

You’ll note that this is a session that has been doing quite a lot of work. I was watching it because I wanted to check that it was only generating undo in a series of very short recursive transactions. (It’s running a coalesce on a very large, very smashed, index).


WordPress allows me to see statistics about “referrers” – the places that people came from before getting to my blog. This can be interesting, and potentially useful, information.

From time to time the referrer is the “WordPress Dashboard” – which I think means that my blog has appeared on the WordPress front page as one of the more popular blogs on  That’s a rather nice feeling. In fact some recent stats on WordPress say that it gets a little over 2 billion page views per month on 11.4 million blogs. Since my blog currently gets about 50,000 page views per month I’m responsible for about 1/40000 of the total page views … which is well above average.

There is a downside, though, to appearing on the WordPress dashboard – there seems to be an interesting correlation between the days I hit the WordPress dashboard and the days when I see spam comments climb to high values; fortunately Akismet manages to filter out almost all the spam, but I wonder if there are packages on the market that keep checking for popular blogs then automatically start generating spam comments on them.

But let’s move on to a more worrying referral: a couple of days ago the thing that appeared top of the list was a domain name starting with “freesexmovie”. I didn’t try clicking on it to discover what was at the far end – I took a guess, and I’m always a little paranoid about picking up viruses (of the computer kind) from strange web sites. I struggled, though, to find the connection between Oracle and something being free.

Is this another case of clever software finding popular blogs and creating local references to them, perhaps copying unusual words or phrases, so that search engines will lead unsuspecting readers to the wrong sites ?

There’s probably a suitable “bon mot” that I could quote for both these referral observations – but I can’t think of one at present.

Oracle Closed World: last minute additions Exadata any MySQL talks

We've just added talks on Exadata and MySQL starting at 1:15-2pm today.

In summary

1:15-2pm Exadata and MySQL

2pm Gwen Shapira on webscale, /dev/null

3pm Kevin Closson on SMT and Flash (

Beer served the whole time and lunch around 2:30

Oracle Closed World 1-4 Thirsty Bear, Sept 22, 2010, directions

Stanley at OOW 2010

Yesterday, on Tuesday September 21st, I met with Debra Lilley, Robyn Sands, Mogens Norgard and Dan Norris at the Chevys. When we exited I took some funny pictures of Dan, Debra and Mogens and, of course, Stanley-Oracle ACE Director. And I'm pretty sure everybody knows Stanley. If not, go to his home page and learn more about him.

Exadata V3 – Oops – EXADATA X2-8

Oracle had the new version of the Exadata Machine on display at Oracle Open World this week. It’s called the Exadata X2-8. That’s a catchy name. It sounds very Iron Manish! In fact they had these fellows on display next to the demo machines.

The X2-8 uses two 4U Sun Fire x4800 servers which each have 8 x eight-core intel CPUs (X7560) and 1 Terabyte of memory along with 14 Exadata Storage Servers. Here’s a link to the spec sheet for the X2-8 and for the Oracle Sun X4800. Below are a couple of pictures. The first one shows one of the database servers (X4800) with one of the CPU modules out.

The storage cells have not changed much from the original V2. They still have 2 CPUs and 12 drives and 384G of flash cache. Although I’ve been told they have newer (faster) 6 core Intel CPUs. (I did get a look at an unpublished spec sheet on an Oracle employee’s iPhone and it said they were using the 5670 CPUs) Oh, and they will allow you to run Solaris on the database servers. Of course they will have to finish a new version of Solaris 11 before that can happen. It’s worth noting that X2-8 can be ordered but that they don’t have a firm delivery date yet.

So this configuration is definitely for the high end market and addresses a couple of issues. The increased memory will allow us to have a more robust consolidation platform. It will also allow bigger OLTP type systems to run better (i.e. the additional memory means we can support many more concurrent users and have much larger buffer caches). Note that Exadata’s offloading generally reduces the memory requirements, but nevertheless, very large systems, particularly ones with lot’s of fast OLTP type transactions and lot’s of users will be better satisfied by this type of configuration. Also note that there is no little brother version of the X2-8. It comes in a full rack only. Which makes sense because there are only two database machines. I don’t believe the price has been set yet, but the word on the street is that the hardware will be about 50% more than the full rack version with the small 2 CPU blades (now renamed X2-2 by the way).

I did a post a couple of weeks ago (Thoughts on Exadata V3) about what I thought we might get to see in the way of Exadata changes. We got most of the things I was expecting but not all of them. Among the things we got are bigger/beefier servers with more memory and available slots for HBAs to provide some additional connection capabilities (although I’m not sure if Oracle is going to want people to open the machines up and put additional controllers in). I did see mention in the x4800 spec sheet of an HBA so they may actually have one in there already (I need to check that out). They also announced that they will be offering a version of Solaris that can run on the database servers which I was expecting, although they are still using Intel chips. The thing I was expecting that didn’t happen was a change of mind set about flexibility of configuration. They seem pretty set on maintaining a fixed configuration that will be the same for every customer. That is probably not such a bad idea. Certainly it’s easier to support and faster to deploy. But you know how customers are, they want their hamburgers with extra mustard and no pickles. So we’ll see how that works out over time. But for now, it’s a fixed menu. To quote Henry Ford, “You can get it in any color you want as long as it’s black”.

So that’s all I can think of at this point. Please let me know if you have any questions and I’ll see what I can find out.

Oracle OpenWorld Day 3 Highlights

  Started Day 3 waking up at 3am and staying awake until San Francisco decided to slowly light up. I have a feeling this summary will be a little briefer than previously … First up was my Unconference Q & A session at Parc 55 Hotel. Considering the overall “Javaness” of the venue and location, I was actually [...]

My Oracle Open World 2010 Presentation - "Query Transformations"

This year I have a presentation titled "Query Transformations" in Moscone South, Room 300 on Thursday, September 23 at 12:00. In last years I had done a similar presentation several times at different conferences. However, this presentation contains new transformations which came in Oracle 11gR2. The list of query transformations I will talk about is the following:

–JPPD - join predicate push-down
–FPD - filter push-down
–PM - predicate move-around
–CVM - complex view merging
–SPJ - select-project-join
–SJC - set join conversion
–SU - subquery unnesting
–OBYE - order by elimination
–CNT - count(col) to count(*) transformation
–JE - Join Elimination
–JF - join factorization

Especially the last one added in 11gR2 is quite interesting and has the background in the patent registration application which could be found here. Another very interesting source of information is the paper presented by several Oracle employees at VLDB'09 which is available here. During the whole presentation I am showing excerpts from CBO trace file in order that the audience can learn how CBO reports about performed transformation. Some useful pieces about transformations are also available in Optimizer Development Team blog.

According to number of enrolled attendees it looks like the room will be almost full. Yesterday I had a discussion with Mohamed Zait who is in the Optimizer development team and he was surprised that the topic about query transformations is so interesting for OOW attendees. My personal opinion shared also by many others is that the content of too many presentations at OOW contains just a "helicopter" view of what is available but doesn't show or explain anything what is going on "behind the scene". However, with great pleasure I must admit that I was able to find some very good presentation during last 3 days what just confirms the fact that the speakers feel the need to go beyond the "usual" level of expertize and I am very thankful for that. One of such presentation was prepared by Maria Colgan titled "Explaining the Explain Plan: Interpreting Execution Plans for SQL Statements" where I haven't heard some new stuff but liked very much the way she presented the topic and the contents of the presentation. One of the very important messages she gave was that people should not change database parameters unless they really know what they are doing. She especially mentioned famous OPTIMIZER_INDEX_COST_ADJ which should be left at it's default value of 100. I was missing at least some words about system statistics. The other one I found also very interesting was "Oracle Database Performance Secrets Finally Revealed" presented by Greg Rahn and Michael Hallas.

My presentation is available for downloading at my home site. You have to login in (or register first if you have no login yet).

OpenWorld Day 1-3…

This years OpenWorld has been a little unusual for a couple of reasons. First, in previous years the OTN Lounge (now The Zone) and the Unconference have been in Moscone West, which meant it was really easy to bounce between those and the database sessions in Moscone. This year The Zone and the Unconference venue are near the Hilton, which make for a lot of walking and clashing sessions for anyone with a database focus. I guess the extra walking will do us all good. :)

Second, the wifi this year has been really bad. There are always glitches, and don’t get me started on the schedule builder, but this year the wifi has been unusable for extended periods of time. In fact, I’ve never managed to get on it in Moscone South yet. It makes life very difficult when you are trying to use an online schedule builder. :(

Enough of the moaning. Let’s focus on the good…

The best thing about being at OpenWorld is all the cool people you meet. Lots of new faces and lots of old friends. I’ve also really enjoyed The Zone this year. At first the location and layout felt a little odd, but I’m now used to it and it feels even more relaxing than previous years. I’ve been hanging around there a lot, chatting to people rather than trying to attend every conference session on my agenda. Most importantly I won the Google sponsored Lego competition today. I play with Lego a lot with my nephews, so I felt like I had an unfair advantage. :)

I’ve been quite selective about the sessions I’ve attended, picking speakers I enjoy listening to more than specific topics. With so many conferences under my belt over the last couple of years it’s getting harder to find sessions with new content, but that’s a nice problem to have. :)

The evenings have been as fun as ever. The ACE dinner was on a boat this year. Food, drink and unsteady footing didn’t sound like the best idea. As it turned out it was really good fun. Especially since the water was calm. The OTN party was a food fest. I’m sure other things were happening, but all I can really remember was eating. :) Tonight was a quick trip out with some of the guys, then back to the hotel to catch up with the blogging.



PS. I bought an iPad. More to come on that as I learn how to use it, or not…

I Shall Wear Midnight…

I Shall Wear Midnight is the most recent book in the Discworld series. It’s a continuation of the Tiffany Aching story line and like the other Young Adult books, doesn’t have such a densely packed story line. It was enjoyable, but didn’t rock my world.