Oracle

dbakevlar's picture

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.

oradebug's picture

Oracle RMAN Restore to the Same Machine as the Original Database

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.

arupnanda's picture

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.

dbakevlar's picture

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.

oraclebase's picture

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…

oraclebase's picture

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. :)

oraclebase's picture

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.

Jonathan Lewis's picture

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:

Jonathan Lewis's picture

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:

Jonathan Lewis's picture

Cache anomaly

Just a quick heads-up for anyone who likes to play around with the Keep and Recycle caches.

In 11g Oracle introduced the option for serial direct path reads for tablescans on tables that was sufficiently large – which meant more than the small_table_threshold – provided the table wasn’t already sufficient well cached.  (The rules mean that the choice of mechanism can appear to be a little random in the production environment for tables that are near the threshold size – but if you try testing by doing “alter system flush buffer_cache” you find that you always get direct path reads in testing.)

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