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Observing Oracle Exadata SmartScan internals, part 1

In order to look how Exadata smartscans are different, first let’s have a peek the Oracle full segment/multiblock read evolution as short as possible:

a) Traditional multiblock reads, visible via the event ‘db file scattered read’
The essence is: Multiple adjacent blocks are read from disk, and put in the buffercache. Because every read is sequentially processed, IO latency is a performance penalty for every physical read. This works roughly this way: get a set of adjacent blocks from the segment header, fetch these blocks from disk, process these blocks, then get the next set of adjacent blocks, fetch these blocks from disk, process these blocks, etc.

Listing Exadata storage cells and their configuration info from V$CELL_CONFIG

If you attended my Exadata hacking session today, you saw me using the cellver.sql script which lists some basic configuration info about the currently connected storage cells:

Enkitec’s Exadata Smart Flash Cache Hacking Session by Tanel Poder! (free stuff!!!)

We recently received our 3rd Exadata machine into Enkitec’s exalab. Now we have a V2, X2 and X3 there, in addition to ODA, Big Data Appliance (which comes with a beer-holder built in!) and an Exalytics box! So you understand why Karl Arao is so excited about it :-)

This occasion demands that we hack the hell out of all this kit soon! So, let’s have another (super-secret) hacking session!

This time, let’s see how the Exadata Smart Flash Cache works! (both for reads and writes). Note that we won’t cover Smart Flash Logging in this session (otherwise we’ll end up spending half a day on it :)

Friday Philosophy – Level of Presentations

This FF is a bit of a follow-up to the one I posted last week on PL/SQL skills and a comment made by Noons on how much knowledge you need to be an OakTable member.

I have a question to answer and I would appreciate other people’s opinion. Should there be more intro talks at conferences? If so, should the experts be giving them?

ExaSnapper 0.7 beta download and the hacking session videos

Thank you for attending the Exadata Snapper (ExaSnapper) hacking session!

I have split the recording of this session into 3 pieces and uploaded to The ExaSnapper v0.7 beta that I demoed is also available now at (registration needed). See the links below.

For quick reference, here’s the syntax of running ExaSnapper – there are two modes, one is the before/after capture (think Tom Kyte’s runstats, but for exadata metrics) and the other is more like a DBA-monitoring mode, where you can just measure a few seconds worth of a long-running query runtime and get the IO and efficiency figures from there.

Here’s an excerpt from the install script documentation section:

Drilling Deep Into Exadata Performance with ASH, SQL Monitoring and Exadata Snapper – slides and a hacking session!

The promised hacking session about Exadata performance troubleshooting will happen on Thursday 21st February 9am-11am PST (2 hours). I will show a number of examples and demos where the Exadata Snapper shows what was going on in storage cells when running Smart Scans or just doing IO.

Register here (free stuff!):


I will post the scripts on the day of this session.

How to Troubleshoot OEM 12c Cloud Control Auto-Discovery

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I was recently involved in an upgrade project to go from to on an Exadata V2. We hit some snags during the upgrade specifically related to OEM 12c Cloud Control. We performed an out-of-place upgrade and OEM had some difficulty in dealing with this.

12c Cloud Control is supposed to run a daily check that looks for new targets on each server. When it finds something new, it places this in a queue to wait for admin approval. With a single click, you can promote the newly discovered target to an OEM managed object.

RMOUG – Here I Come

Well, I’ve just finished pushing the last few bits into my suitcase for my trip to the US for the Rocky Mountain User Group Training Days 2013.

It is a few years since I went to the US for pleasure (3 years?) and much longer since I went there on a combined work/pleasure trip – as I HATE going through US immigration.

Storage Indexes vs Database Indexes Part III: Hidden Values (Hide Away)

OK, my holiday to Hawaii is now slowing fading away into distant memory. Time for a new post In my previous post on differences between Exadata Storage Indexes and Database Indexes Part II, I discussed how the clustering of data within the data is an important factor (pun fully intended !!) in the performance and […]

Enkitec Extreme Exadata Expo (E4) 2013 – Call for Papers

Enkitec E4, the only exclusively Exadata-focused conference in the world, is going to be back this this year too! :-)

It will take place on 5-6 August 2013 in Four Seasons Hotel & Resorts in Irving, TX. It will be very hot in Texas then, but the hotel has a really cool pool there (which I intend to be able to use this year – last year I had to spend all my free time working in the hotelroom unfortunately). And they have beer inside too :)

There will be very good speakers showing up this year too (including the keynote speaker who’s awesome, but I can’t say the name yet) and I’ll hang out there too. I think I’ll deliver a live demo / internals hacking session this year (that way I don’t have to spend my night before the conference preparing slides and can focus more on the cool stuff).