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September 2014

Unusual Deadlock

Prompted by a question on OTN I came up with a strategy for producing an ORA-00060 deadlock that DIDN’T produce a deadlock graph (because there isn’t one) and didn’t get reported in the alert log (at least, not when tested on It’s a situation that shouldn’t arise in a production system because it’s doing the sorts of things that you shouldn’t do in a production system: but possibly if you’re trying to do some maintenance or upgrades while keeping the system live it could happen. Here’s the starting code:

Oracle Database – Getting started with JSON Path Expressions

Yesterday my colleague Alex and I had the pleasure to do some extra presentations during AMIS’s Oracle OpenWorld preview evening. While still not getting around...
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Embiggening the Marquee Menu Dots

The Marquee template on the Squarespace platform is wonderful with it's colorful images and parallax scrolling on index pages. It's one of my top two favorite templates. What's not so wonderful sometimes are those tiny dots in the parallax navigation menu at the right side of the browser window. 

The tiny targets in the parallax menu can be tough to hit with a mouse pointer, and a lot of detail or the wrong color in that right-side region can make the fly-out text tough to distinguish from the underlying image. What follows are a series of CSS mods by which you can bring some zest to that menu while making it into a larger and more legible target. 

Embiggening the Marquee Menu Dots

Building your Squarespace website in the Marquee template? Having trouble
seeing or clicking on those little dots that make up the parallax
navigation on the right side of your browser window?...

Read the full post at

inmemory: Why did that table was not populated in the column store?

I enabled an huge 70G table for inmemory population, I expected the inmemory population to take a while, but the population didn’t complete even after letting it run for a day. Why?

ASH data

Initial review of the server shows no issues, no resource starvation. This must be a problem with Oracle processes itself. I started digging further, and ASH data shows that in numerous samples the process was seen reading block using single block I/I calls. Also object_id matches with the table I was trying to populate.

inmemory: sa00 process

After the restart of a 12c inmemory database with 300GB+ SGA, I noticed that an Oracle background process sa00 was consuming a bit of CPU. Documentation suggests that it is SGA Allocator process, however, ipcs -ma command shows that the shared memory segment is already allocated. I was curious, of course, what would that background process will be allocating?.


Process stack of the process shows that it is touching SGA pages to pre-page SGA memory pages.

Inmemory: Not all inmemory_size is usable to store tables.

I have been testing the inmemory column store product extensively and the product is performing well for our workload. However, I learnt a bit more about inmemory column store and I will be blogging a few them here. BTW, I will be talking about internals of inmemory in Oaktable world presentation, if you are in the open world 2014, you can come and see my talk:


Can you have high redundancy files in a normal redundancy diskgroup?

One of the perks of teaching classes is that I get to research questions asked. In the last Exadata Administration Class I taught someone asked: can you have your disk groups in Exadata on normal redundancy yet have certain databases use high redundancy? This would be a good interview question …

The answer is yes, which I remembered from researching material on the 11g RAC book but I wanted to prove that it is the case.

Update: I planned a second blog post where I wanted to test the effect but Alex Fatkulin was quicker, and I promise I didn’t see his post when I wrote mine. Otherwise there probably wouldn’t have been one :) In summary, you aren’t really any better protected. The disk group remains at normal redundancy, even with the data files in high. Looking at Alex’s results (and I encourage you to do so) I concur with his summary that although you have a 3rd copy of the extent protecting you from corruption, you don’t have higher resilience.

The primary election is over. Sadly, I did not win.

Either the power of social networking is not yet up to the task of overcoming television ads and the visual and other pollution of yard signs EVERYWHERE, or New Hampshire is not ready for the #SAFE_DEAL and to #IMPOVERISH_DRUG_LORDS. (Or, I suppose, they just didn’t like me. Quickly figuring my likely exposure, though, I believe a large percentage of folks who heard my message actually voted for me. So maybe I just need to get better and spreading the word at low cost. I do find it ironic that MAYDAY pac endorsed a candidate who did spend money on the grounds he pledged to fight against large campaign media budgets in the future, while I operated on a minimal media budget. Notice that is not a criticism of the candidate they did endorse.)

Anyway, completely cribbed from WMUR-TV’s site, here are the apparent 99% returns:

Brown, Scott 58,635    50%  Rubens, Jim   27,048 23%  Smith, Bob     26,483 23%

VirtualBox 4.3.16

virtualboxVirtualBox 4.3.16 has arrived. The downloads and changelog are in the usual places.

Although 4.3.14 worked fine on OS X and Linux, I skipped it on Windows because it just wouldn’t start a VM. That issue is allegedly fixed in this release. The changelog includes the following entry.

Windows hosts: fixed startup problems on certain Windows hosts due to conflicts with anti-virus software (4.3.14 regression, bug #13187)”

Happy days! :)