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.

For quite some time I used to have a configuration file /etc/yum.repos.d/public-yum-ol7.repo managing my package sources in lab VMs. Today I noticed that this configuration file is deprecated, and has been replaced by a new model. This is explained in the Oracle Linux 7 administrator guide and a few other sources I totally missed. I thought I’d show you the full story in this post before I go and change all my Ansible scripts :)

State of play before

To repeat the scenario I just went through, I created a new machine, server3, based on the stock Oracle Linux 7.6 image. After its initial boot I log in to the console to perform a yum upgrade.

I have been talking about Vagrant for a long time and use it extensively on my Ubuntu-powered laptop. I am using Oracle Linux 7.6 for most of my lab builds, and I like to have specific tools such as collectl, perf, and many others available when the VM boots. I als like to stay in control of things, especially when it comes to downloading otherwise unknown things from the Internet I decided to learn how to create a Vagrant box myself.

I recently made an interesting observation while monitoring database performance on an Oracle Enterprise Edition system. While looking at some ASH data (for which you must be licensed appropriately!) I came across direct path reads attributed to a select statement performing a primary key lookup. At first, this didn’t make much sense to me, but it’s actually intended behaviour and not a bug.

In this post I’m reproducing what I observed. I am using Oracle 18.4.0 for this experiment running on my Linux lab environment. The hardware uses 1s8c16t with 64 GB of memory.

For a little while now I have been using Ansible for all installation/configuration tasks I do in the lab. I can’t really be bothered to do these things by typing commands anymore: once you get the hang of Ansible, you can develop an urge to automate everything. As part of my playbook installing the Oracle database on Oracle Linux, I replace /etc/yum.repos.d/public-yum-ol7.repo with the current version from Oracle’s server to make sure I have the latest and greatest software available.

This post is about how to manage grub2 in an easy way.

grub1

In the past, which is before linux EL7, the boot loader was grub, the grand unified bootloader (version 1). Things were very simple; if you installed another kernel (using rpm) it would add an entry to grub’s configuration in /boot/grub/menu.lst. If you wanted to change grub to boot that newly installed kernel by default you edit /boot/grub/menu.lst and set ‘default’ to the number, counting from zero, of the newly installed kernel, in the order of the kernels listed. If you wanted a certain option set for booting the kernel, you added it to the kernel line.

I haven’t used Data Pump in a little while but recently needed to do a bit of work involving this very useful utility to export a single table. I know that it is possible to export data in parallel using expdp, but I can’t recall the syntax for doing so off the top of my head when I need it. This post describes a potential approach to exporting a table in parallel. In the next post I will demonstrate an interesting case where using parallelism didn’t help me speed up the export. All of this was tested on 12.2 and 18.4.0, the examples I am sharing originate from my 18.4.0 single instance database (without ASM) running on Linux.

The setup

My lab environment is a bit limited when it comes to storage, so I’ll have to do with small-ish tables. The basic principles should still apply for larger segments though. Please note that my tables aren’t partitioned to keep the individual segment size as large as possible. 

There are a few alternative ways of installing Ansible on Linux, and the install guide for Ansible 2.7 (the current version at the time of writing) does a great job in explaining them all in detail.  There is a potentially easier way to get to a current Ansible version if you are using Oracle Linux 7, but it comes with a very important limitation. Let’s get that out of the way first.

Agenda: https://www.techdaysbelgium.be/?page_id=507

Dates: February 7 and 8, 2019

Location: http://cinemacartoons.be in Antwerp, Belgium

More information soon.

For people from the netherlands: this is easy reachable by car or by train! This is a chance to attend a conference and meet up with a lot of well-known speakers in the Oracle database area without too extensive travelling.

At the time of writing Oracle’s Cloud Infrastructure as a Service (IaaS) offers 2 ways to connect block storage to virtual machines: paravirtualised and via iSCSI. There are important differences between the two so please read the documentation to understand all the implications. I need all the performance I can get with my systems so I’m going with iSCSI.