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December 2013

Cloning databases

My friend Kyle wrote a blog piece a while back

http://www.kylehailey.com/what-delphix-does-in-1-minute-22-seconds/

Now, not to criticise Delphix (in fact,the opposite – its a very very cool product, and you should read some of Kyle’s great blog content on it), but if you have not got it, or can’t get it, then as long as you have some imagecopy backups, and a NFS server hanging around, you can get to the "next best thing" using Oracle’s Direct NFS feature.

So…how close can we get to 1 minute 22 seconds…Lets try on a laptop :-)

number of set bits

 

declare
  n number := ....;
  tmp number;
begin
  tmp := n - ( bitand ((n / 2) ,3681400539))
           - (bitand ((n / 4) ,1227133513));
           
   tmp := mod ( bitand ((tmp + (tmp / 8)) , 3340530119) , 63 );
  dbms_output.put_line(tmp);
end;

Google for "hakmem" to see how it works

EM12c- Managing Incidents, Stopping the Insanity, Part III

Nothing is more annoying that getting alerted on things that are not critical to you or that you already know is occurring and there is not a darn thing you can do about it.

EM12c- Managing Incidents, Stop the Insanity Part II

So what do you do when network hiccups and other “small” issues start to send you incident notifications that a target is down, when in fact, it was really about a target just being delayed in communicating with the Oracle Management Server, (OMS)?

These are just one more way that “white noise” can drive a DBA to pull their hair out.

Parameterizing Hive Actions in Oozie Workflows

Very common request I get from my customers is to parameterize the query executed by a Hive action in their Oozie workflow.
For example, the dates used in the query depend on a result of a previous action. Or maybe they depend on something completely external to the system – the operator just decides to run the workflow on specific dates.

There are many ways to do this, including using EL expressions, capturing output from shell action or java action.
Here’s an example of how to pass the parameters through the command line. This assumes that whoever triggers the workflow (Human or an external system) has the correct value and just needs to pass it to the workflow so it will be used by the query.

Here’s what the query looks like:

Upgrading to Oracle Linux 6.5

This is a very short post to demonstrate how to upgrade to Oracle Linux 6.5. My lab system was reasonably current, Oracle Linux 6.4 with some security patches (but not all). The upgrade to 6.5 (or “latest”) is very simple, and since Oracle announced they had beefed up connectivity it’s a real joy. Instead of 450kb/s I get around 9 MB/s. For those of you who want the ISO image: you can’t currently get it from edelivery, the only update method is YUM/ULN or you download the ISO from My Oracle Support, patch 17860279.

Friday Philosophy – The Passing of Nelson Mandela

As this is a blog on the technical aspects of the Oracle RDBMS and management in IT, it is not really the correct place to pass comment on the passing of a political figure, let alone touch on the politics of race and discrimination.

But I don’t care, it’s my blog and I can do what I want.

I’m partly saddened by the death of Nelson Mandela even though I never met him as I think he was one of those rare things – a politician who was actually a good person who was trying to right wrongs. Thus I think humanity has lost a very good human. But he had been suffering from very poor health for a long time and maybe he would have been happy for it to come to an end. I do not know of course.

[Oracle] SQL*Net researching - Setting Session Data Unit (SDU) size and how it can go wrong

Introduction

I come across this SDU issue from time to time by doing oracle database consulting work and so i think it is worth to write a blog about it. Basically this blog is about how to verify that the SDU setting is considered (or not) at all. It also covers some basics and SAP suggestions.

 

Lets' start with an explanation and some SAP information about the SDU, before we go on with researching and testing several settings.

 

The Harmonic Mean

The arithmetic mean is what you learned in school. However, it is the
harmonic mean that is often - but not always! - the correct choice when
computing an average over a collection of rates.



Read the full post at www.gennick.com/database.

The Harmonic Mean

The arithmetic mean is what you learned in school. However, it is the
harmonic mean that is often - but not always! - the correct choice when
computing an average over a collection of rates.



Read the full post at www.gennick.com/database.