Search

Top 60 Oracle Blogs

Recent comments

January 2014

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.

Public Speaking Tip 10 : Watch other speakers!

A really good way of improving your presentation skills is to watch other speakers. I will often go to sessions by people who I know to be good speakers, just to watch their technique. It’s actually easier if it is a session you’ve seen before, or on a subject you don’t have much interest in, so you can focus on the presentation skills, not the content. :) There are a few speakers I try to get to see at every conference, having seen the same presentation several times for this very reason.

CR Trivia

Everybody “knows” that when you do a tablescan of a table that it starts with two buffer gets on the segment header, though older versions (ca. 8i and earlier) of Oracle used to do 4 buffer gets on the segment header. The upshot of this is that many people still say that if you create a table and insert a single row then you’re going to get 3 buffer gets when you tablescan a table: two for the segment header and one for the data block:

So here’s a test, with the second set of autotrace stats which, for reasons I’ll describe shortly, may not be immediately reproducible on your system:

HCC error on Exadata after partitioning maintenance

Recently I have been asked to investigate the following error on an Exadata system.

ORA-64307: hybrid columnar compression is not supported for tablespaces on this storage type

Well, that’s simple I thought! Must be (d)NFS mounted storage, right? Everyone knows that you can have HCC on Exadata (and a few other storage products). So I looked at the problem and soon found out that the data files in question all resided on the cells. Here is the sequence of events:

Public Speaking Tip 9 : Feedback helps you improve!

In yesterday’s post I was kind-of dismissive of feedback, in so far as not letting it ruin your performance on the day. Once the sessions is over, that is the time to reflect on your performance and start looking for feedback. Feedback and advice from others is the best way to decide what you need to work on to improve.

Many conferences ask their attendees to fill in speaker evaluations and make the results available to speakers. The actual marks don’t always tell you too much, but the written comments can be very interesting. They tend to focus on extremes, people who either love or hate you. Even so, it’s worth checking this stuff out to see if there is something obvious you need to work on.

12c Online Partitioned Table Reorganisation Part I (Prelude)

First post for 2014 !! Although it’s generally not an overly common activity with Oracle databases, reorganising a table can be somewhat painful, primarily because of the associated locking implications and the impact it has on indexes. If we look at the following example: So we have a table with a couple of indexes. We […]

LOB changes

It’s always useful to collect baseline information – especially when it helps you notice that the baseline has moved in a way that might explain the next performance problem you see. Here’s an example demonstrating the benefit.

I have a table with a LOB column that is stored out of line. Many years ago I decided that I wanted to compare how the redo generation varied as I change the LOB from cached to nocache (with nologging). So here was one of my simplest test scripts (stripped to a minimum):

Monitoring Application TCP traffic on Mac

viamoi

photo by Stuart Williams

My internet provider said my service was degraded due to the large amount of data uploading from my computer. As far as I knew, my computer wasn’t uploading anything but I didn’t know how to prove it.

I decided to try and write a DTrace program to look at it. (I also installed “Little Snitch” which seems pretty cool).

Public Speaking Tip 8 : You can’t please all the people all the time!

Provided your title and abstract accurately describe what you are presenting (see deliver what you say you will), you’ve got to trust the audience have made the right choice to come to your talk. Frits Hoogland made this comment on that previous post.

“It works the other way around too… Got a comment on a deep dive presentation saying ‘stuff way over my head’…”

This was my response to Frits.

“You did what you said you would. They picked the wrong session. Not your fault!”

If you describe a session as a “deep dive” and a newbie comes to it, they can’t complain about it being to complicated. If you describe a session as an introduction, experts can’t complain that it didn’t go into enough depth.