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Some ideas about Oracle Database on Docker

By Franck Pachot

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This is not a ‘best practice’ but just some ideas about building Docker images to provide an Oracle Database. I started with the images provided by Oracle: https://github.com/oracle/docker-images/tree/master/OracleDatabase/SingleInstance and this is great to validate the docker environment. Then I customized for my needs and here are the different points about this customization.

Do not send a huge context at each build attempt

I work by iteration. Sending a 3GB context each time I try a build is a no-go for me. Then I quickly stopped to put the Oracle installation .zip in the context of my build. I already blogged about this.

20 Indexes

If your system had to do a lot of distributed queries there’s a limit on indexes that might affect performance: when deriving an execution plan for a distributed query the optimizer will consider a maximum of twenty indexes on each remote table. if you have any tables with a ridiculous number of indexes (various 3rd party accounting and CRM systems spring to mind) and if you drop and recreate indexes on those tables in the wrong order then execution plans may change for the simple reason that the optimizer is considering a different subset of the available indexes.

FBIs don’t exist

This is a reprint (of a reprint) of a note I wrote more than 11 years ago on my old website. I’ve decided to republish it on the blog simply because one day I’ll probably decide to stop paying for the website given how old all the material is and this article makes an important point about the need (at least some of the time) for accuracy in the words you use to describe things.

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There’s no such thing as a function-based index.

Well, okay, that’s what the manuals call them but it would be so much better if they were called “indexes with virtual columns” – because that’s what they are and that’s a name that would eliminate confusion.

ADWC – the hidden gem: Zepplin Notebook

By Franck Pachot

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In the previous blog posts I explained how to create, and stop/start the Autonomous Data Warehouse Cloud service. And I didn’t show yet how to connect to it. It is easy, from sqlplus or SQL Developer, or SQLcl.

But there’s something more exciting to run some SQL queries: the Oracle Machine Learning Notebooks based on Apache Zepplin. At first, I didn’t realize why the administration menu entry to create users in the ADWC service was named ‘Manage Oracle ML Users’, and didn’t realize that the ‘Autonomous Data Warehouse Cloud’ header was replaced by ‘Machine Learning’.

FBI Limitation

A recent question on the ODC (OTN) database forum prompted me to point out that the optimizer doesn’t consider function-based indexes on remote tables in distributed joins. I then spent 20 minutes trying to find the blog note where I had demonstrated this effect, or an entry in the manuals reporting the limitation – but I couldn’t find anything, so I’ve written a quick demo which I’ve run on 12.2.0.1 to show the effect. First, the SQL to create a couple of tables and a couple of indexes:

StarEast, InteropITX and GDPR

I’m getting ready to get on a plane between two events today and have been so busy, that there’s been a break in blogging.  That’s right folks, Kellyn has let a few things slide….

ADWC – a Docker container to start/stop Oracle Cloud services

By Franck Pachot

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In the previous post, I’ve explained how to start and stop the Autonomous Data Warehouse Cloud service from PSM (PaaS Service Manager). There’s a setup phase, and a run phase starting with service-start and ending with service-stop. And the setup is specific to an Oracle Cloud account, storing information in the local user home. You may want to run different setups, and even provide an easy way to start/stop an Oracle Cloud service without knowing the user, password and tenant name.

A Docker container is perfect to isolate this.

ADWC: start/stop with PSM Command Line Interface

By Franck Pachot

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In the previous post, I explained how to create an Autonomous Data Warehouse with PSM (PaaS Service Manager Command Line Interface). The most common operation you want to do with it is starting and stopping the service. This is the best way to save credits for hourly billed services. And PSM is the easiest: run from everywhere (it is Python 3) and no need to provide credentials each time. In the previous post, I explained how to setup PSM for the ADWC service.

Unfortunately, for starting and stopping the instance you may realize that:

ADWC: Creation of Autonomous Data Warehouse Cloud service

You want to try the Autonomous Data Warehouse Cloud Service? That’s easy. Here is a Step-by-Step.

A look into oracle redo, part 11: log writer worker processes

Starting from Oracle 12, in a default configured database, there are more log writer processes than the well known ‘LGWR’ process itself, which are the ‘LGnn’ processes:

$ ps -ef | grep test | grep lg
oracle   18048     1  0 12:50 ?        00:00:13 ora_lgwr_test
oracle   18052     1  0 12:50 ?        00:00:06 ora_lg00_test
oracle   18056     1  0 12:50 ?        00:00:00 ora_lg01_test

These are the log writer worker processes, for which the minimal amount is equal to the amount public redo strands. Worker processes are assigned to a group, and the group is assigned to a public redo strand. The amount of worker processes in the group is dependent on the undocumented parameter “_max_log_write_parallelism”, which is one by default.