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August 2020

Vagrant Box Drama

I had a little bit of VirtualBox and Vagrant drama today.

I was doing my normal thing of recreating some test VMs and I started to get errors like this during the first part of the VM build, before the config scripts ran.

Introducing packer: building immutable infrastructure in the cloud

After having spent a bit of time with Packer to create Vagrant base boxes it was time to focus on the cloud. I have referenced Packer multiple times in my cloud talks as a popular way to create immutable infrastructure and/or custom images, and I wanted to share how you could potentially make use of the technology

Be aware that this is a post about cloud technology. If you are following along, be aware that you will incur cost.

Tracing Errors

This is a little lesson in trouble-shooting. It assumes you have the privilege to generate and edit trace files, and all I’m going to do is show how I worked out the answer to a fairly simple question that appeared recently on the Oracle Developer Community forum in a thread with the title  Cannot drop table after start dropping unused columns checkpoint.

I have a table t1 which is reasonably large (1M rows) with a column v30, and I’ve issued the command.

AWR Flush Levels

From version onward, for taking AWR snapshots, you have the choice between four AWR flush levels: BESTFIT, LITE, TYPICAL and ALL. If you check the Oracle Database documentation, you won’t find much information about the difference between them. The best you will find, in the PL/SQL Packages and Types Reference, is the following:

The flush level can be one of the following:

How to control resource usage on Autonomous

When you connect to your Autonomous Database, you get to choose from some predefined services. The services available depends on whether you are using a transaction processing (ATP) or a data warehouse instance (ADW) of the database, but for example, for an ATP database you get the following:


Note: This is a screen of the docs as of time of writing this post. Over time, that may change so always be sure to consult the docs directly in future.

FK on delete

This is part 1 of a short reference note about the work load created by referential integrity constraints when you delete from a parent table. It was prompted by a question on the Oracle Developer Community forum about how to handle a very large delete from a table which (a) included a column of type CLOB and (b) had 9 child tables.

The 9 referential integrity constraints were declared with “on delete cascade”, but the delete was taking too long even though all the related child data had been deleted before the parent delete. In outline the process was designed to operate in batches as follows:

How to make queries to DBA_FREE_SPACE faster

The other day as my PC popped up its usual “Hey, you really should look at buying a bigger disk” Smile message, I was motivated to see if I could clear down some of the space utilization on the myriad of databases on my machine. On the majority them I encountered no issue doing that, but on one of them, the query to DBA_FREE_SPACE revealed an odd performance issue:

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Data virtualization on SQL Server with Redgate SQL Clone

By Franck Pachot

In the previous blog post I’ve installed SQL Server on the Oracle Cloud. My goal was actually to have a look at Redgate SQL Clone, a product that automates thin cloning. The SQL Server from the Oracle marketplace is ok for SQL Clone prerequisites. There’s a little difference in .NET Framework version (I have 4.6 where 4.7.2 or later is required but that’s fine – if it was not an update would be easy anyway).