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December 2012

Database Virtualization

What is database virtualization? Database virtualization, as opposed to operating system virtualization, is sharing a read only copy of a source database between clone databases. The clone databases are called virtual databases (also called thin provision clones as distinct from full physical copy clones).  Virtual databases are much more than simple read only databases. The virtual databases can also write to the data files. How can the virtual databases write to the data file when the data files are read only? Writing to the data files is accomplished either through one of two basic mechanisms. Those mechanisms are block pointer copy on write file systems or journal file systems. When a virtual database writes to the data files the changes are not written to the data file but are kept in a private area only visible to that virtual database. Each virtualized database sees what appears to be a private read/write copy of the database.

Who Stole gettimeofday() System Calls From Oracle strace() sessions?

I’ve been meaning to write this blog post for a while now but never seemed to find the time. Hopefully this posting will be useful information for anyone that spends a lot of time tracing processes in Oracle from the Linux Operating System. I’m one of those people, so it was good to get to … Continue reading "Who Stole gettimeofday() System Calls From Oracle strace() sessions?"

Who Stole gettimeofday() System Calls From Oracle strace() sessions?

I’ve been meaning to write this blog post for a while now but never seemed to find the time. Hopefully this posting will be useful information for anyone that spends a lot of time tracing processes in Oracle from the Linux Operating System. I’m one of those people, so it was good to get to … Continue reading "Who Stole gettimeofday() System Calls From Oracle strace() sessions?"

Who Stole gettimeofday() System Calls From Oracle strace() sessions?

I’ve been meaning to write this blog post for a while now but never seemed to find the time. Hopefully this posting will be useful information for anyone that spends a lot of time tracing processes in Oracle from the Linux Operating System. I’m one of those people, so it was good to get to … Continue reading "Who Stole gettimeofday() System Calls From Oracle strace() sessions?"

Storage Indexes vs Database Indexes Part I MIN/MAX (Maxwell’s Silver Hammer)

It’s often stated that in Exadata, you don’t need conventional database indexes anymore as everything runs so damn fast that indexes are simply a waste of time and space. Simply drop all database indexes and things will run just as fast. Well, not quite … There are many many scenarios where database indexes are still […]

Why is it easier to get things to work at home?

I’ve been grabbing a few minutes here and there over the last couple of work days trying to get something working with no joy. I this case it is a DAD entry in the “dads.conf” file on the OHS running as part of 11gR2 Forms & Reports Services on WebLogic 11g (10.3.6). I started to think that maybe this functionality is disabled on the installation or something like that, but couldn’t find any reason for that to be the case.

In a fit of desperation I came home tonight, fired up a DB and a F&R installation, defined a DAD and it worked first time. Aaaarrrggghhhh!!!!!

On the plus side, I know there is nothing fundamentally weird about the OHS installation that comes with 11gR2 F&R Services. On the down side, I still have no flippin’ clue why it is not working on the installation at work. Think I need to get in early tomorrow and focus on it for a little while. No doubt it will be something stupid I’ve missed while trying to do a bunch of different things at once.

Dbvisit Reporting…

I try to stick close to core Oracle technologies and steer clear of product endorsements, but over the years I’ve bumped into the ladies and gents from Dbvisit a number of times and they have been consistently cool and consistently on the money with their products. At Oracle OpenWorld 2012 I bumped into Arjen Visser who told me about their new product called Dbvisit Reporting, so I asked him to keep nagging me until I tried it out. When we met at UKOUG 2012 I still hadn’t tried it, but he had been too polite to bug me about it. This weekend it made it to the top of my list. :)

Throttling IO with Linux

Why?

I guess the first question which comes to mind when reading this title is ‘Why’? For a database, but I guess for any IO depended application, we want IO’s to be faster, not throttle them, alias make them slower. Well, the ‘why’ is: if you want to investigate IO’s, you sometimes want them to slow down, so it’s easier to see them. Also, (not so) recent improvements in the Oracle database made great progress in being able to use the available bandwidth by doing IO in parallel, which could strip away much of the ability to see them in Oracle’s popular SQL trace.

Tom Kyte in Moscow – 2

On December 11th Tom Kyte performed “AskTom in Moscow” for the second time (first time was almost three years ago in February 2010). I was there and enjoyed presentations, tweeted a lot about the content and in the end I’ve won a signed copy of the Expert Oracle Database Architecture (2nd edition, in Russian)!

The start

A glass for questions. It was full in the end of the day

Small mishap with this website…

Sorry, for those who where missing, or needed, some of the info here yesterday. Due to a small mishap regarding an incorrect URL update, some annoying redirects occurred. :S