Author: Christo Kutrovsky

Correction on Storage Index Blog

This is just a quick post to note that I’ve corrected my blog on Storage Indexes here, after a follow up blog from Kerry Osborne indicating an error on my part.

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Oracle Exadata HCC Removes the 255 Columns Limit

As a follow up from my previous post on Exadata Design, where I question the use of dimensions for certain attributes in data warehouses, I figured I should test whether HCC works with tables that have more than 255 columns, It does. Here’s my test case.

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Designing for Exadata: Maximizing Storage Indexes Use

Oracle Exadata V2 is a very well balanced database machine combined with smart and innovative software. One of these innovative features is the Storage Index – a game changing feature in my opinion.As with any feature, there are intended use cases, limitations and caveats. Use it right, and amazing performance gains can be achieved. Use it wrong, and nothing will happen. This is what is great about storage indexes in particular. They are there, without any overhead. It’s only a question of how to leverage them, in addition or combination withevery other feature that Oracle Exadata has to offer.

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Oracle’s OPT_ESTIMATE hint: Usage Guide

Many have expressed the deepest desire to see OPT_ESTIMATE documented, but that never happened. I’ve just troubleshot a problem and used this hint a lot during my “what if” scenario testing, and found this hint to be quite useful. Thus, I decided to document it here on the blog. I will come back and update this blog as I discover new parameters, and feel free to suggest what you’ve found in the comments. If you can, include an example to illustrate usage.

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RAC+ASM 3 years in production. Stories to share (slides from RMOUG10)

Here are the slides from my presentation at RMOUG 2010. I am not sure how much sense all this will make without my comments. We may do it in a webinar if there is sufficient interest. Regardless I will probably be doing it again at some point in the future.

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Oracle Parallel Query Sorting and Index Creation Performance Problems

There’s a serious performance bug that’s been in Oracle for a while, and finally there are hints of it been fixed, but only partially. The bug happens when performing sorting operations in parallel, and the source data is already well sorted. The “ranger” doesn’t do a good job of properly assigning row ranges to sorter processes, and ~90% of the rows end up being sent to the same parallel process, regardless of the level of parallelism.

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Adding Columns with Default Values and Not Null in Oracle 11g

Oracle 11g has a new performance enhancement when adding columns. In the pre-11g releases, adding a new not null column with a default value would have caused a massive update on the entire table, locking it for the operation and generating tons of undo and redo. I’ve seen this happening in production. Oracle 11g has improved this behaviour by storing the default value in the metadata and making the column addition instantaneous. Although this is a welcomed enhancement, there are some unexpected aspects beyond the basic operations. First, we know default values for new columns are stored in the metadata, but what happens when you change the default?

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RMOUG: Day Two

Day 2 finished yesterday. It was quite a busy day, with some excellent sessions. Have a look.

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RMOUG: Day 1

Day One at RMOUG in Denver is now over. There were quite a few interesting presentations. Unfortunately, the very first I went to was canceled due to car trouble. I also found that several sessions of similar interest to me overlapped, so I had to choose my spots. I provided a detailed breakdown of the sessions I attended here.

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Christo Kutrovsky Presenting at RMOUG

I am back on the road, going to RMOUG Training Days to present The Answer to Free Memory, Swap, Oracle, and Everything. I am quite excited, as the RMOUG schedule looks quite promising.

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