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February 2019

Friday Philosophy – Size is Relative

The below is a USB memory stick, a 64GB USB memory stick which I bought this week for about 10€/$. I think the first USB memory stick I bought was 8MB (1/8000 the capacity) and cost me twice as much.

The death of UTL_FILE – part 2

I wrote a post a while back call “The Death of UTL_FILE”, and probably because of it’s click-bait title I got lots of feedback, so I’m back to flog that horse Smile. Seriously though, I stand behind my assertion in that post, that the majority of usages of UTL_FILE I’ve seen my career are mimicking the spooling behaviour of a SQL*Plus script. And as that post pointed out, you can now achieve that functionality directly with the scheduler.

That is well and good for writing files from the database, and I added:

Use the features available!

Advance warning: This post is a just another normal Friday morning rant. If you’re not interested in my pontificating, move along…nothing else to see here Smile

Sometimes you can’t make use of a facility that you normally would, and you have to substitute in something else. For example, if I would normally take the train to the basketball game, but today it’s not running due to track maintenance, then I’ll take the bus. I have no problem with that, because there’s a reason that I can’t take the train that day.

What does get my goat is on a day when the train is running, you come to me and say:

Network troubleshooting with tcpdump and strace

Here is a little example using tcpdump and strace to troubleshoot a network issue with an Oracle connection. It may not be the best approach for all cases, but just an example, as this is a copy/paste of my screen after I analyzed it. I just changed the server names.

At some point, the communication between two servers was hanging, with both endpoints waiting on read() — like ‘SQL*Net message from client’ wait event on the server. This issue occurred only on some circumstances: a case that always reproduced was RMAN correctly connected to the catalog, but hanging when we did a ‘show all’.

Client netstat and strace

I have RMAN started and connected to the catalog.

I identify my client process, in this case the RMAN executable. I display its TCP connection with netstat and its current system calls with strace:

Ansible tips’n’tricks: understanding your Ansible configuration

When writing automation scripts I tend to use a local Ansible configuration file. This has certain advantages for me, such as including it in a version control system (VCS). It also is a valid option for developers without access to the global configuration file installed by the package manager. And more convenient to use than setting environment variables.

WARNING: There are some very important security considerations though, which you must be aware of before using a local configuration file.

Until now I haven’t spent a lot of time thinking about configuration variables and the order of precedence, but that is exactly what I’d like to do in this post.

DBMS_JOB is an asynchronous mechanism

One of the very cool things about DBMS_JOB is that a job does not “exist” as such until the session that submitted the job is commits the transaction. (This in my opinion is a critical feature that is missing from the DBMS_SCHEDULER package which, other than this omission, is superior to DBMS_JOB in every way).

Because DBMS_JOB is transactional, we can use it to make “non-transactional” things appear transactional. For example, if part of the workflow for hiring someone is to send an email to the Human Resources department, we can do the email via job submission so that an email is not sent if the employee record is not created successfully or is rolled back manually, eg:

Learning About Oracle in Belgium

It’s always so good to see a user community growing. Last week was the first ever technical conference for obug (or is it OBUG) – the Oracle Benelux User Group. It was an excellent couple of days, packed with a fantastic range of presenting talent and an enthusiastic audience. I was honoured to be asked to be one of the presenters.

Work Life Travel balance

I thought about writing a post on juggling work commitments, travel with my job and time at home with children and family. And then I came across this post from community friend Robin Moffatt.

https://rmoff.net/2019/02/08/travelling-for-work-with-kids-at-home/

“Oracle Indexing Internals and Best Practices” Seminar – Berlin 8-9 May: DOAG Website

Just a short note to say that DOAG have now a registration page for my upcoming “Oracle Indexing Internals and Best Practices” seminar running in Berlin, Germany on 8-9 May 2019. For all the details regarding this acclaimed educational experience and how to book your place, please visit: https://www.doag.org/de/eventdetails?tx_doagevents_single[id]=577320 Please mention you heard this seminar […]

Unique Indexes Force Hints To Be “Ignored” Part I (What’s Really Happening)

As I was compiling my new “Oracle Diagnostics and Performance Tuning” seminar, I realised there were quite a number of indexing performance issues I haven’t discussed here previously. The following is a classic example of what difference a Unique Index can have over a Non-Unique index, while also covering the classic myth that Oracle sometimes […]