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January 2012

gc cr disk read

You might encounter RAC wait event ‘gc cr disk read’ in 11.2 while tuning your applications in RAC environment. Let’s probe this wait event to understand why a session would wait for this wait event.

Understanding the wait event

Let’s say that a foreground process running in node 1, is trying to access a block using a SELECT statement and that block is not in the local cache. To maintain the read consistency, foreground process will require the block consistent with the query SCN. Then the sequence of operation is(simplified):

OT: Do Search Terms Describe the Visitor?

January 12, 2012 I thought that I would start this slightly off topic blog article with a bit of humor.  Seven months ago I wrote a blog article that refuses to move from the first position in the most visited articles on this blog.  In the process of trying to understand why a mathematics focused article [...]

ASH

You may have noticed that I’m having a little trouble keeping up to date on the blog at the moment – I know I’ve got several comments on Oracle Core to respond to but haven’t had time to look at them yet. Very briefly, though, I thought I’d point to a note that Doug Burns has just posted about John Beresniewicz’s presentation one “outliers” at the UKOUG conference.

Key feature: it supplies a query that could be very useful for capturing short, but nasty, events;  and has links to a couple of documents explaining what it’s trying to do and why. It’s a query that could do with more exercise on production systems so that Doug can get some feedback to JB about how effect it is, and how it could be improved.

Start here.

 

You've Got Framing

The framing clause brings the "window" to window functions. It's an ideal
solution when you can arrange a business question such that an answer comes
from applying an aggregate function to a range...



Read the full post at www.gennick.com/database.

You've Got Framing

The framing clause brings the "window" to window functions. It's an ideal
solution when you can arrange a business question such that an answer comes
from applying an aggregate function to a range...



Read the full post at www.gennick.com/database.

RMOUG 2012 – Hello Denver!

On February 14-16, I’ll be at the Colorado Convention Center in Denver, Colorado for RMOUG’s Training Days Conference. This is the largest regional Oracle User Conference in North America and attracts presenters from all around the country and the globe. I’ll be presenting:

Presentation Name: Troubleshooting RAC Background Process

Abstract: RAC background process performance is critical to keep the application performance. This session will demo techniques to review the performance of RAC background processes such as LMS, LMD, LMON, etc. using various statistics and UNIX tools. The presentation will also discuss why certain background processes must run in higher priority to maintain the application performance in RAC.

Presentation Name: A Kind and Gentle Introduction to RAC

Beware of ACFS when upgrading to 11.2.0.3

This post is about a potential pitfall when migrating from 11.2.0.x to the next point release. I stumbled over problem this one on a two node cluster.

The operating system is Oracle Linux 5.5 running 11.2.0.2.3 and I wanted to go to 11.2.0.3.0. As you know, Grid Infrastructure upgrades are out-of-place, in other words require a separate Oracle home. This is also one of the reasons I wouldn’t want less than 20G on a non-lab like environment for the Grid Infrastructure mount points …

Now when you are upgrading from 11.2.0.x to 11.2.0.3 you need to apply a one-off patch, but the correct one! Search for patch number 12539000 (11203:ASM UPGRADE FAILED ON FIRST NODE WITH ORA-03113) and apply the one that matches your version-and pay attention to these PSUs! There is the obvious required opatch update to be performed before again as well.

Dbvisit Standby…

Several years ago I met Arjen Visser and Bertie Plaatsman from Dbvisit and they told me about their standby database product, which is a replacement for Data Guard. Now I don’t spend much time on non-Oracle products, but this one was interesting to me as it works on Standard Edition, unlike Data Guard which is an Enterprise Edition option. From that point onward I kept seeing Arjen and conferences and telling myself I really should take a look at the product.

Over last year I bumped into Arjen at a few conferences, along with some other members of the company (Eric, Mike and Vit). They are a cool group of people, so my interest in their products was ignited again. Finally, after several years of showing interest I tried out the standby product towards the end of last year, which resulted in the following article.

IOTs by the Oracle Indexing Expert

I’m really pleased to see that Richard Foote has started a series on Index Organized Tables. You can see his introductory post on the topic here. As ever with Richard, he puts in lots of detail and explanation and I’ve been a fan of his blogging style for a long time.

I’ve got a few posts on the topic left to do myself, maybe this competition will spur me to get on and write them!

Index Organized Tables – An Introduction Of Sorts (Pyramid Song)

Thought it was high time that I covered in a little detail the subject of Index Organized Tables (IOTs). When used appropriately, they can be an extremely useful method of storing and accessing data. Hopefully by the end of this series, you’ll have a better understanding of IOTs, their respective strengths and weaknesses and so perhaps [...]