Month: November 2013

UKOUG Tech13, Latency Investigations and Lost Writes

I am looking forward to participating again to the UKOUG annual conference. This year I will present together with my colleague Marcin Blaszczyk on two topics that are follow-up of articles in this blog.
The first talk is: Storage Latency for Oracle DBAs. A presentation about a performance tuning techniques for Oracle and storage, based on the study of latency wait event histograms and their representations with heat maps. It will be a good occasion also to show examples of the usage of OraLatencyMap and PyLatencyMap.
The second talk is: Lost Writes, a DBA’s Nightmare? This is a short presentation about lost writes in Oracle, based on our production experience. It’s still surprising to me how such a seemingly unimportant failure class can in reality generate very complex failure and recovery scenarios.
If you are participating to the Tech13 conference, feel free to come and talk to us! Our presentations are on Monday morning (11:30 in the hall Exchange 4/5) and Wednesday morning (9:30 in the Exchange Auditorium).
More presentations at Tech13 by CERN colleagues: “Next Generation GoldenGate vs. Streams for Physics Data“, “Cardinality Feedback Tuning Revisited – Adaptive Query Optimization in Oracle 12c“, “WebLogic as a Service Provider for CERN Web Applications: APEX & Java EE“, “Using SQL Developer to Improve Code Quality

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VirtualBox 4.3.4

Oracle VirtualBox 4.3.4 has been released. The downloads and changelog are in the usual places. I thought 4.3.4 included a fix for the Mac OS X upgrade issue I posted about, but it didn’t. The install of 4.3.4 was seamless and didn’t require any fiddling about. I’m currently running VirtualBox 4.3.4 on Fedora 19, Oracle Linux 6, OS X Mavericks and Windows 7. Cheers Tim…

VirtualBox 4.3.4 was first posted on November 30, 2013 at 11:19 am.
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Hard Drive Predictive Failures on Exadata

This post also applies to non-Exadata systems as hard drives work the same way in other storage arrays too – just the commands you would use for extracting the disk-level metrics would be different. I just noticed that one of … Continue reading

Jean Claude Van Damme : Volvo

One of my friends posted me a link to this great video. I’m a big Jean Claude Van Damme fan and have been since I first saw him in No Retreat, No Surrender. I was at a mates house and I didn’t have access to a couple of Volvo trucks, so I had to use […]

Jean Claude Van Damme : Volvo was first posted on November 29, 2013 at 11:43 am.
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Interesting Plan

A recent question on the OTN database forum included an execution plan that prompted one reader to ask: “but where has the existence subquery gone?” Here’s the original question showing the query, and here’s the later response showing the plan that prompted the question. There were three possible reasons why that question may have been […]

UKOUG Presentations for Tech13

I’m giving 2 presentation this year at the UK Oracle User Group Tech13 Conference The first is a discussion about the reason why you do or do not need to do low level detail traces and block dumps, and argument with Martin Widlake (and the audience hopefully). This is at 4pm on “Super” Sunday 1st. […]


During a performance inspection of some E-Business Suite batch programs running on, I noticed almost 99% of the consistent reads missing in the tkprof file for a particular insert statement. It was a giant INSERT ALL statement where the accompanying select statement contained several subqueries in a "case when exists (query)" construct. And those subqueries in the select clause was what

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