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February 2016

How can I see my invisible columns

A cool new feature in 12c is the ability to make a column invisible.  The concept has existed since 8i to handle things like “set unused” and function based indexes, but now it is available to developers directly.

SQL> create table T ( c1 int, c2 int );

Table created.

SQL> desc T
 Name                          Null?    Type
 ----------------------------- -------- -----------------
 C1                                     NUMBER(38)
 C2                                     NUMBER(38)

SQL> alter table T modify c2 invisible;

Table altered.

SQL> desc T
 Name                          Null?    Type
 ----------------------------- -------- -----------------
 C1                                     NUMBER(38)

So at this point… how I can tell in SQL Plus that I even have an invisible column, without querying the data dictionary.

Oracle Cloud – Stairway to Heaven…?

I was lucky to be granted some Oracle Cloud subscriptions. Today I needed an…

Enterprise Manager 13c, “Webtier Could Not Be Started”

Let’s say you’re on call and you’re woke from a deep, delightful sleep from the pager, stating the Enterprise Manager Cloud Control isn’t available.

Always write everything down!

notes-514998_640In my second job we worked on projects in small teams, maybe 2-3 people. My boss at the time, the team leader, was a lady called Andrea. She wrote everything down. I mean everything! I was still pretty new to the business world and rather naive, so I tended to rely on my memory a lot. Needless to say, she saved our bacon on numerous occasions. That was a very good lesson!

Equi-sized partitions on random data

Had an interesting AskTom question today about dynamically keeping partition sizes in check. The poster had large table, already partitioned, but since there was no logical column to do a range partition on, it was partitioned on a surrogate primary key value. Due to the volatility of the data, (with a BLOB column on the table) evenly sized primary key ranges led to dramatically different partition sizes, causing manageability concerns. Partitions could be split and/or merged, but obviously if those partitions contain data, that is both a very expensive operation, and could impact availability of the data depending on the type of maintenance operation performed.

So the challenge became – can we proactively have (roughly) equi-sized partitions, when we don’t know how and when the data is going to come in.

Something new learned every day

One of the reasons I leapt at the chance to be on the AskTom team when we resurrected the site, was that it’s like free training.  You get questions on topics you have not visited before, and you get new angles on things you thought you already knew.

Just today, someone posted a question about the new DEFAULT ON NULL syntax in 12c, with the following observation:

“Standard inserts advance the sequence only when needed, but a PL/SQL for-loop advances the sequence all the time”

And here was their test case… (Sidebar:  WOO HOO!!! Yippee !!!! A test case !! A test case !!! People get it !!! Smile )

Performance Data Visualization for SLOB. The SLOB Expert Community is Vibrant!

Thanks to Nikolay Savvinov (@oradiag) for his excellent post on how to wrap his scripts around the SLOB test driver ( to capture and produce performance data visualization graphs.  I recommend a visit to his post here:

Performance Data Visualization with SLOB


As always, the link for SLOB is: Obtain the SLOB Kit and Helpful Information Here

The New Smartphone Upgrade

I’ve been feeling quite amorous about the camera features on my Samsung Galaxy 6 Edge phone, but noticed that it wasn’t taking as automatically impressive pictures as usual and sometimes, I even had to focus, (the horror!) I turned the camera over and could see a hairline crack inside the camera lens.  It was a really odd place to have damage, as the exterior cover to the lens was fine.

Oracle Midlands : Webinar

Just a quick reminder about tonight’s Oracle Midlands Webinar.




Oracle Midlands : Webinar was first posted on February 22, 2016 at 10:48 am.
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All change at (MySQL 5.7 and PHP7)

Over the weekend I decided to upgrade from MySQL 5.6 to 5.7. I did some test upgrades a while ago and last week at work we did some practice upgrades on a clone of one of our production servers. I was pretty confident the upgrade would be fine and it was. I wasn’t totally sure how some of the surrounding applications would cope with the change though.

Once the MySQL 5.7 upgrade was complete everything was working fine, so I got a little excited and decided to switch to PHP7 as well. Before this I was just using the stock version from the CentOS6 yum repository, which was pretty old.