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12.2 New Feature: the FLEX ASM disk group part 4

Flex Disk Group Properties

In the previous 3 parts I shared my investigation into ASM Flex Disk Groups, Quota Groups, File Groups, and how Quota Groups actually enforce space limits. What I haven’t discussed yet was changing properties of a File Group and the effects thereof. Properties I have in mind are related to the protection level, as discussed in the official documentation-Automatic Storage Management Administrator’s Guide, Administering Oracle ASM Disk Groups. There are of course other properties as well (and you’ll find a link to all of the modifiable properties later in this post), but they are out of scope for this investigation.

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 group of hosts. Rundeck has an ansible plugin. Using that plugin, it could perform the similar functionality as Ansible Tower (commercial product) or Semaphore (open source).

After a fresh installation of Centos 7, do the following as root:

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 the user ‘prometheus’. In order for that user exist, it must obviously first be created:

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 to inefficient use of memory, especially in today’s world of consolidation.

The information about linux server database usage is available in /proc/meminfo, and looks like this:

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 shorter than the previous two. Had I combined part 3 and 4 it would have been too long for sure … BTW, you can navigate all posts using the links at the very bottom of the page.

Are quotas enforced?

The purpose of the Quota Group is … to enforce quotas on a disk group, much like on a file system. This is quite interesting, because you now have a hard limit to which databases can grow within a disk group even for non-CDBs.

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 implies – will enforce quotas for entities residing within it. It is optional to add one yourself, Oracle creates a default Quota Group for you that does not enforce storage limits. As you will see later, the default Quota Group will be assigned to all new databases in the Flex ASM disk group.

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 information.

This blogpost is intended to show the effects on pages when DML happens. This is inherently different from my personal reference of database implementation, which is the oracle database.

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 aware that this post is about my lab experiments, I have no production experience with FLEX ASM disk groups. As with all new features it might take a while to mature, so test, test, test…

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 and line pointer array. This blogpost looks at the actual tuples, including the index, and how these are stored in the pages.

Postgresql block internals

This blogpost is the result of me looking into how postgres works, and specifically the database blocks. The inspiration and essence of this blogpost comes from two blogs from Jeremiah Peschka: and
I am using Oracle Linux 7u3 and postgres 9.6 (current versions when this blogpost was written).

Postgres is already installed, and a database cluster is already running. Let’s create a database ‘test’ for the sake of our tests:

$ createdb test

Once the database is created, logging on is done with ‘psql’: