How to Checksum Downloads

As a DBA, in your time, you will need to download files such as Oracle binaries, patches, etc.  As a rule of thumb, you should always checksum you downloads, to ensure they are free of corruption.  In my example, I needed to download:

This is the Quarterly Full Stack Download Patch for Exadata, which is 10 zip files that (more...)

Disable SELinux on Oracle Linux 7

Sometimes when I want to test something or write a prototype of some sort SELinux (Security-Enhanced Linux) kicks in and hinders me, given that it is enabled by default on OL 7 UEK 4. STOP! Before I let you continue to read take a mental note of my disclaimer: I am an advocate of having … Continue reading "Disable SELinux on Oracle Linux 7"

Installation of Rundeck with the Ansible plugin on Centos 7

This post shows you how to install Rundeck with the Ansible plugin on Centos 7. The installation is done with nginx as the web server and using SSL with a self signed certificate. Please read the Ansible installation script, and modify anything that should be different for your situation. You will be amazed how well readable the installation script is!

Rundeck is a web based user interface that allows you to run commands against a (more...)

Installation overview of node_exporter, prometheus and grafana

Prometheus is an open source systems monitoring and alerting toolkit originally build at Soundcloud. This blogpost shows how to install the needed components to do visualisation of linux system statistics via Grafana.

The setup consists of 3 components:
node_exporter, an exporter of system and hardware metrics.
prometheus, a metric collection and persistence layer.
grafana, the visualisation layer.

1. Preparation
The needed components are installed in the home directory of (more...)

Linux memory usage

One of the principal important configuration settings for running an Oracle database is making appropriate use of memory. Sizing the memory regions too small leads to increased IO, sizing the memory regions too big leads to inefficient use of memory and an increase in memory latency most notably because of swapping.

On Linux, there is a fair amount of memory information available, however it is not obvious how to use that information, which frequently leads (more...)

12.2 New Feature: the FLEX ASM disk group part 3

In the previous 2 parts of this mini series I introduced the Flex ASM disk group and two related concepts, the Quota Group and File Group. In what should have become the final part (but isn’t) I am interested in checking whether quotas are enforced.

(Un)fortunately I have uncovered a few more things that are worth investigating and blogging about, which is why a) this isn’t the last post and b) it got a bit (more...)

12.2 New Feature: the FLEX ASM disk group part 2

In the first part of this series I explained the basics and some potential motivation behind the use of ASM Flex disk groups. In this part I would like to complete the description of new concepts.

New Concepts related to FLEX ASM Disk Groups

With the Flex disk group mounted, the next steps are to create a few new entities. First, I want to create a Quota Group. The Quota Group – as the name (more...)

Postgresql block internals, part 3

This is the third part in a series of blogposts about how postgresql manages data in its blocks (called ‘pages’ in postgres speak). If you found this post and did not read the previous ones, it might be beneficial to read block internals (part 1) and block internals, part 2 first. In these blogposts I’ve shown how heap and index pages look like, and how these can be investigated, including looking at the raw block (more...)

12.2 New Feature: the FLEX ASM disk group part 1

I knew about the 12.2 FLEX ASM disk group type from other presenters but until now – when researching the feature for the upcoming DOAG HA Day – I haven’t been able to appreciate how cool this is. And I really think it is pretty cool and worth sharing! There is a lot to be said about the feature and these tests, which is why I am splitting it into multiple parts.

Please be (more...)

Postgresql block internals, part 2

This is the second part of a blogpost about Postgresql database block internals. If you found this blogpost, and are interested in getting started with it, please read the first part, and then continue with this post.
I am doing the investigations on Oracle Linux 7u3 with postgres 9.6 (both the latest versions when this blogpost was written).

In the first part I talked about the pageinspect extension, and investigated the page header (more...)

Installing App Designer on Ubuntu

It’s been a while since I have tried to install Application Designer directly on my Linux host. In fact, the last time I tried was many tools versions ago. Since I’ve been playing with a PUM again, it’s time to give it another try.

Here’s my notes:

Installing Wine

I figured that my best chance at getting App Designer to work was to use the latest version of Wine. So, I used the repository to (more...)

JDBC, Linux and Entropy

Some troubles — especially those happening only sporadically — are not so easy to shoot and call for a deeper understanding of the matter. In the following real-world example this means: SQL*Net Tracing and some knowledge about the inner workings of the server’s operating system, particularly random number generation. This case was suited well to demonstrate an approach to trouble-shoot […]

Oracle Linux: Clean Yum dbcache

These weeks we provide a course on Weblogic 11g and 12c Basic and Advanced Administration and Tuning & Troubleshooting. We use an Oracle Linux 6 VM with a Database and Weblogic 11g and 12c.

We got some complaints (issued in a friendly way, by the way) from the attendees that a filesystem of the VM got filled up.

One of the attendees found out that the following folder containt some very large files:

-rw-r--r--. (more...)

Oracle Enterprise Linux – Pre-Built for Enterprise

We've shared the AMI we use for running Oracle Enterprise Products like e-Business Suite. You'll find it on the AWS Marketplace pre-loaded with all the pre-requisites you need for your Oracle implementation on AWS.

Link to the Marketplace...

#Javaland 2017 wrap up

Yes – I did it again and attend Javaland conference in Phantasialand Brühl.

It was not easy this year to concentrate on the sessions because of the hottest march of the last 100 years. But the quality of the sessions beats the weather. Maybe again my invest in reading the abstracts and filter the sessions before the conference has payed off.

Day 1 Conference

Jens Schauderdocumentation & slides with AsciiDoc, Git, Gradle and Reveal.js


Enable HyperFIDO U2F Key on Linux

Recently, I bought the Hypersecu HyperFIDO K5 Key to help me secure access to several websites and services with U2F (“Universal Two-Factor Authorization”). This works fine on Windows, but with Linux things get a little complicated: The key isn’t accessible to all users by default. This has to be activated using udev rules, which is widely […]

Using VS Code for PL/SQL development

I've been using Sublime Text as my main editor for PL/SQL development for many years, but I'm now in the process of switching to Visual Studio Code (VS Code).

Some good reasons to use VS Code:
  • Multi-platform (Windows, OS X, Linux)
  • Free, open source
  • Lightweight, fast
  • Large ecosystem of extensions
  • Built-in Git support
  • Can be adapted to PL/SQL coding via a plsql language extension (syntax highlighting, go to/peek definition, go to symbol) and PL/SQL compilation (more...)

Oracle Linux Update from 7.2 to 7.3 crashes with uncorrectable CPU error

During the Upgrade of Oracle Linux 7.2 to 7.3 with “yum update”, when updating the microcode_ctl package, the system crashed and firmware reported an uncorrectable CPU error after reboot.

It turned out that the update of the package in combination with specific Intel CPUs causes the issue. In the meantime, there is a red hat bug and solution available.



  • MOS: The system could (more...)

I’m speaking at Advanced Spark Meetup & attending Deep Learning Workshop in San Francisco

In case you are interested in the “New World” and happen to be in Bay Area this week (19 & 21 Jan 2017), there are two interesting events that you might want to attend (I’ll speak at one and attend the other):

Advanced Spark and TensorFlow Meetup

I’m speaking at the advanced Apache Spark meetup and showing different ways for profiling applications with the main focus on CPU efficiency. This is a free Meetup in San Francisco hosted (more...)

Creating a RAC cluster using Ansible (part 2)

In my previous 2 blogposts i explained how to setup a Vagrantfile that deploys 2 virtualbox machines that can be used as a basis for a RAC cluster and how you could use Ansible to deploy RAC on those VM’s. In this post i want to dive a bit deeper into how i setup Ansible and why, keep in mind that this just one way of doing this.

The Github repository containing all the files (more...)