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January 2014

Oracle X$ tables – Part 1 – Where do they get their data from?

It’s long-time public knowledge that X$ fixed tables in Oracle are just “windows” into Oracle’s memory. So whenever you query an X$ table, the FIXED TABLE rowsource function in your SQL execution plan will just read some memory structure, parse its output and show you the results in tabular form. This is correct, but not the whole truth.

Check this example. Let’s query the X$KSUSE table, which is used by V$SESSION:

Oracle X$ tables – Part 1 – Where do they get their data from?

It’s long-time public knowledge that X$ fixed tables in Oracle are just “windows” into Oracle’s memory. So whenever you query an X$ table, the FIXED TABLE rowsource function in your SQL execution plan will just read some memory structure, parse its output and show you the results in tabular form. This is correct, but not the whole truth.

Check this example. Let’s query the X$KSUSE table, which is used by V$SESSION:

Oracle X$ tables – Part 1 – Where do they get their data from?

It’s long-time public knowledge that X$ fixed tables in Oracle are just “windows” into Oracle’s memory. So whenever you query an X$ table, the FIXED TABLE rowsource function in your SQL execution plan will just read some memory structure, parse its output and show you the results in tabular form. This is correct, but not the whole truth.

Check this example. Let’s query the X$KSUSE table, which is used by V$SESSION:

Applying PSU 12.1.0.1.1 to Oracle Restart

I was actually hoping I had already written enough about applying the PSU for 12.1.0.1.0 but today I tried to apply the patch to my Oracle Restart home in my lab VM and guess what-it wasn’t as automatic as I thought.

I must have performed the classic copy & paste error and applied the patch to the GRID_HOME only. Please don’t do this! The README clearly states you can but if you do, you will run into this mess. At the time of writing there was no hit for the error on my favourite search engine, hence this post. If you see this on a real database and not on your personal lab VM you should of course consult support what to do. This is for educational purposes only, so to say.

Public Speaking Tip 12 : Why Bother?

In some ways, this should have been the first post in the series, since there are probably a number of people out there who don’t care about speaking at conferences. In my opinion everyone should try their hand at public speaking, because it gives you numerous transferable skills.

I guess a number of people in the Oracle community who know me will laugh at this following statement, but I am naturally a shy person and although I like to talk to people on a one-to-one basis, speaking in groups is not natural for me. I always hated having to read things out loud in class. If I was asked to introduce myself in a meeting, I would get that “butterflies in the stomach” feeling and have a bit of a panic. There are two ways you can react to this. You can avoid putting yourself in those situations, or you can confront your fear and go for it. I chose the latter.

Dates in A Range

I revisit the problem of returning a row for each day in a month, and
generalize the solution to return rows for any desired range of dates. Then
I go further and explore how to return multiple...



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

Dates in A Range

I revisit the problem of returning a row for each day in a month, and
generalize the solution to return rows for any desired range of dates. Then
I go further and explore how to return multiple...



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

Public Speaking Tip 11 : International presentations

As a native English speaker, life is pretty easy for me when presenting around the world. Oracle is an American company, so people are used to having to deal with English speaking presenters. Either the audience speak English already, or the events and audience expect to use a translation service. Even so, I often joke that when I’m presenting in other countries I’m still having to translate what I say on the fly, because my everyday language is not really suitable for an international audience. :) In this post I’ll look at some of the things you need to look out for when speaking in other countries. Some will be equally relevant to other English speaking nations.

Volume of information and speed of presentation

Quick Tip on Using Sqoop Action in Oozie

Another Oozie tip blog post.

If you try to use Sqoop action in Oozie, you know you can use the “command” format, with the entire Sqoop configuration in a single line:


    ...
    
        
            foo:8021
            bar:8020
            import  --connect jdbc:hsqldb:file:db.hsqldb --table TT --target-dir hdfs://localhost:8020/user/tucu/foo -m 1
        
        
        
    
    ...

This is convenient, but can be difficult to read and maintain. I prefer using the “arg” syntax, with each argument in its own line:

Oracle Midlands #1 : My first presentation of the year done

I wrote a post in November about an Oracle Midlands group Mike McKay-Dirden was setting up, modelled on the free meetups he’s experienced with the SQL Server community. Last night was the first event, with myself and Pete Finnigan speaking.