Search

OakieTags

Who's online

There are currently 0 users and 31 guests online.

Recent comments

Oracle

Frequently Misused Metrics in Oracle

Lying Businessman

Back in March of last year I wrote an article on the five frequently misused metrics in Oracle: These Aren’t the Metrics You’re Looking For.

To sum up, my five picks for the most misused metrics were:

EM12c Auditing

Lately I’ve been having more discussions on securing the EM12c environment.  All of IT has a tendency to treat the Enterprise Manager as a afterthought in both hardware allocation, as well as security best practices.  No one is sure of exactly why this is-  they all have their theories, but we do know it happens often.

Oracle RMAN Restore to the Same Machine as the Original Database

class="l-submain">
class="l-submain-h g-html i-cf">

Among the most critical but often most neglected database administration tasks is testing restore from backup. But sometimes, you don’t have a test system handy, and need to test the restore on the same host as the source database. In such situations, the biggest fear is overwriting the original database. Here is a simple procedure you can follow, which will not overwrite the source.

Collaborate14 Session: The Art and Science of Tracing

Thank you all for coming to my session "The Art and Science of Tracing" at Collaborate 2014. As I mentioned, I prepared a full session even though this is supposed to be a quick tip. I hope you enjoyed it and get the value from the full presentation deck.

You can download

The slide deck
The scripts (this is a zip file. Right click and then Save As ...)

As always, your feedback will be immensely appreciated.

Presentation Slides for IOUG Collaborate

I know that folks have been having some challenges downloading my slides from Collaborate for a couple of my sessions and I know I’ve received errors when updating two of them the other day, so I’ve added them to my slideshare location for your convenience.

OUGN : Summary

With the exception of a 5+ hour layover in Amsterdam, the trip home was pretty straight forward. I flew to Amsterdam with Lonneke DikmansRonald Luttikhuizen and Roel Hartman. During my rather excessive layover, I played catchup with all the internet stuff I missed during the trip… :)

I must say OUGN 2014 was a pretty cool event all round! The speaker lineup was incredible. The location (on a boat) was fun. I’ve not done that for a while. In addition to the presentations, I got a lot of time to talk to people about technology, which is what I love doing, so that made me happy…

OUGN : Day 2

Day 2 started really early. Having got to bed about 02:00, I was up at 05:30 and thinking about my 08:30 session. The previous evening’s conversation with Brynn was playing on my mind a little (in a good way), thinking how that conversation should/would affect my session. The session itself seemed to go well. I enjoyed it anyway. :)

OUGN : Day 1

The journey to Norway was pretty straight forward, but during the second flight, from Amsterdam to OSLO, my nose and eyes started to stream. I didn’t feel ill, but I was starting to worry I might be getting ill right before a conference. I landed in Norway, got the train to the centre of OSLO and walked to my hotel. I was meant to go out to dinner, but I figured bed might be a better option…

The next day we met up and headed off to the boat to begin the conference. After boarding, we went to the keynotes. Since these were in Norwegian, a few of use ended up at the back of the room chatting. :) As soon as I got access to my room I headed on up to check it out. I’ve been on one of these ferry/cruise ships before and I think they are kind of cute.

NVL() change

One of the problems of functions is that the optimizer generally doesn’t have any idea on how a predicate based on function(col) might affect the cardinality. However,  the optimizer group are constantly refining the algorithms to cover an increasing number of special cases more accurately. This is a good thing, of course – but it does mean that you might be unlucky on an upgrade where a better cardinality estimate leads to a less efficient execution plan. Consider for example the simple query (where d1 is column of type date):

select	*
from	t1
where	nvl(d1,to_date('01-01-1900','dd-mm-yyyy')) < sysdate

Now, there are many cases in many versions of Oracle, where the optimizer will appear to calculate the cardinality of

nvl(columnX,{constant}) operator {constant}

as if it were:

NVL() change

One of the problems of functions is that the optimizer generally doesn’t have any idea on how a predicate based on function(col) might affect the cardinality. However,  the optimizer group are constantly refining the algorithms to cover an increasing number of special cases more accurately. This is a good thing, of course – but it does mean that you might be unlucky on an upgrade where a better cardinality estimate leads to a less efficient execution plan. Consider for example the simple query (where d1 is column of type date):

select	*
from	t1
where	nvl(d1,to_date('01-01-1900','dd-mm-yyyy')) < sysdate

Now, there are many cases in many versions of Oracle, where the optimizer will appear to calculate the cardinality of

nvl(columnX,{constant}) operator {constant}

as if it were: