Author: Alex Gorbachev

Oracle Coherence vs. Oracle RAC or Coherence + MySQL = MySQL RAC?

I came across Oracle Coherence today. Seems like this is another approach to clustering than Oracle RAC. Seems like this is a way to scale middle tiers that require shared data without actually using the central database for that. On the other hand, looks like a clustering framework with rules defined by developers as opposed to Oracle RAC that is designed and built to be a black box delivering database services. Has anyone (yeah, I’m asking developers reading the blog) played with it and knows how it feels?

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MSDBF 07: Final Wrap Up

A few days ago, I did a short post about the start of the Miracle Scotland Database Forum 2007. I decided to wait until getting back home to complete a full-blown description of the event. I should warn you, this will be quite lengthy, so draw a deep breath.

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Miracle Scotland Database Forum – Day One

Yesterday was the opening and I should say it was great — nice tour on the Whiskey Heritage Center and couple interesting and humorous sessions delivered by Jonathan Lewis and Graham Wood combined with whiskey tasting. The evening obviously continued after that but you can assume that anyway if you know what I’m talking about.

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Getting ready for MSDBF 2007 but “Go Sens Go”

If you are following my blog then you might recall that I’m going to make a presentation on the Miracle Scotland Database Forum 2007. My presentation is called RAC load testing adventures and it’s based on a project I’ve been through with one of our clients.

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Block Change Tracking Internals: X$ Tables Research

With this post, I’m starting a series about Oracle Block Change Tracking internals. The feature was introduced in Oracle 10 Release 1. I have already published my past presentations and the white paper about that. When I first started, I tried to dig at least something from Metalink, but the public notes contained no implementation details. What I extracted is some pieces of bug texts, and from there I concluded that fixed tables starting with X$KRC are most probably related to the BCT feature.

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21-hours Phantom SELECT Causing ORA-1555 ‘snapshot too old’

One of our clients had an ORA-1555 “snapshot too old” error two nights in a row. The quick and dirty fix would be to increase the retention_period and the potential size of the UNDO tablespace. I was looking at it together with Dave, my new team mate, and a small detail popped up right away — Query Duration=76584 — 21+ hours? I checked the retention period, and it was 2 hours, so the dirty fix would probably fail unless it’s very dirty — dumping undo retention to something like a day and blowing the UNDO tablespace, and still without guarantee that the query finish within a day.

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IOUG Collaborate 07: Oracle Block Change Tracking Internals

I first presented on Oracle 10g Block Change Tracking Internals at UKOUG 06 in Birmingham. It was very well received, but there were quite a few gaps in my knowledge, and I later discovered I was incorrect in some places. I’ve done some additional research, filled in the blanks and corrected in a few places. Download it here.

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IOUG Collaborate 07: Oracle 10g Grid Control

Looks like our blog has turned into a MySQL blog over this week, so I have to do something about it. Luckily, I have zillions of pending posts, so I’ll start with posting my presentations materials from this conference with my remarks on how it went in general.

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Review of Hotsos Symposium 2007

I enjoyed the event and the venue very much. The presentations very generally very good, and to my surprise some of them were somewhat lighter than I would expect. However, that might actually play positively in extending the audience — there are only so many freaks interested only in hardcore performance and internals.

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Miracle Scotland DBF 2007

Unfortunately, I’m too slow to blog about news and can never make it first. Today is no exception and Doug Burns has already posted about “one of the best Oracle Conferences of all times”: I can tell you – I’m so excited to see all those bright people presenting. It’s especially a pleasure to see that Doug (who recently joined my team here at Pythian) is presenting there.

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