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June 2015

CBO Series

About a year ago I came across a couple of useful articles from Stefan Koehler, which is when I added his name to my blog roll. As an introduction for other readers I’ve compiled an index for a series of articles he wrote about the CBO viewed, largely, from the perspective of using Oracle to run SAP. Today I realised I hadn’t got around to publishing it, and there’s been a couple of additions since I first started to compile the list.

Testing 12c CDB Resource Plans and a little bit about OEM Express

Inspired by Sue Lee’s presentation at Enkitec’s E4 conference I decided to re-run my test suite to work out how you can use Database and I/O Resource Manager in Oracle to help consolidating databases in the new Multi-Tenant architecture. I should point out briefly that the use of Multi-Tenant as demonstrated in this article requires you to have a license. Tuning tools shown will also require you to be appropriately licensed…


A new challenge…

After the last 16 years in the contracting and consulting world, for dozens of clients in Australia and other countries around the world, its time for a change of direction.  Whilst doing work with Oracle systems has always been (and continues to be) rewarding, I realised that a lot of the motivation for being at client sites was the sharing of information with developers and DBA’s at those clients so they could get the most out of their Oracle investment.  Similarly, its really cool to speak at conferences to let people explore the Oracle technology in perhaps way they had not thought of, and similarly, blogging about features and idiosyncracies that we stumble upon.  Whatever the medium (and even whatever the technology, whether it be Oracle or otherwise), the concept of an “IT community”, ie, people being keen to share, debate, and discuss has always been one of the things I like about my profession.

12c Parallel Execution New Features: PX SELECTOR

Continuing my series on new 12c Parallel Execution features: I've already mentioned the new PX SELECTOR operator as part of the new Concurrent UNION ALL feature where it plays a key role.

Optimizer curiosity in

For almost as long as I can remember, the optimizer has had a nifty little trick when you (in effect) try to combine two different usage models within a single SQL.  To explain that, I’m referring to the common scenario of: "If a bind value is provided by the caller, then use it, otherwise it shouldn’t limit the result set.  So we commonly see queries like:

select *
where COL1 = NVL(:mybindvar, COL1)

[For ease of discussion, we’ll assume COL1 is not nullable]

Anyway, the nice little optimizer trick was to optimize the query to handle the two separate use cases, so you see a CONCATENATION step in the execution plan, and two FILTER’s, one to handle the case when the bind variable is null, and one to handle the case where it is provided. 

Site maintenance and how to manage changing URLs

DiagnosticsAfter my recent rants about Oracle changing URLs and breaking stuff, I’ve actually done some changes myself. :)

From time to time change is forced on internet content producers. This might be because of platform changes, or changes in the way search engines behave. The important thing is how you handle that change.

EM has been announced!

The latest version of Enterprise Manager, EM, has been announced! The announcement can be seen here. Obviously, there will be a number of posts that come out about it over the next few weeks, so I’ll add this post here as a quick notification and will update it with links to more information as it becomes available.

Technical Articles

Managing the Hybrid Cloud with Oracle Enterprise Manager – Demo
A First Technical Look At Hybrid Cloning in EM12c Release 5

OT: How to interview an Oracle DBA candidate (NOT)

Yesterday T.J. wrote on the Oracle-L mailing list : “ For those of you who have conducted job interviews, what sort of questions have you found to be effective in evaluating a candidate’s skill level?”
I remember the interview at which I could not answer the question “how do you enable block change tracking in a database?” (The answer is “ALTER DATABASE ENABLE BLOCK CHANGE TRACKING.”)
I remember the time when I could not get hired at Google because...(read more)

Cross-platform database migration

Last weekend, we faced one of the larger challenges that we’ve faced in my time at my current client.  Migrate multiple database systems, across multiples sites, all to new hardware (with new endian format), new database version (…and of course, try to do it with as small a disruption to the service as possible.

We are not a Goldengate customer, so pursuing a zero-downtime migration was not considered, and to be honest, even we had such facilities at our disposal, I think we would still have taken a small outage just to allow a "quiet time" to do verification checks etc.

Friday Philosophy – Flippin’ Technology

Sometimes I think I would have been a Luddite or a member of other groups who have trashed new technology in frustration. Some days, I can just scream at it. You would think having worked in Information Technology for so long would make me more of a fan, but it actually makes me worse – as I know there is no need for there to be so much wrong with the electronic dross we all have to deal with day-to-day. And if I, someone who has used (heck, even programmed) computers for 3 decades, have trouble with these damned things, how frustrating must “normal” people find it?