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March 2019

Comparison between #Oracle and #Exasol

After having worked with both databases for quite some time, this is what I consider to be the key differences between Oracle and Exasol. Of course the two have much in common: Both are relational databases with a transaction management system that supports the ACID model and both follow the ANSI SQL standard – both with some enhancements. Coming from Oracle as I do, much in Exasol looks quite familiar. But let’s focus on the differences:

Strengths

Oracle is leading technology for Online Transaction Processing (OLTP). If you have a high data volume with many users doing concurrent changes, this is where Oracle shines particularly.

Exasol is leading technology for analytical workloads. If you want to do real-time ad hoc reporting on high data volume, this is where Exasol shines particularly.

External table preprocessor on Windows

There are plenty of blog posts about using the pre-processor facility in external tables to get OS level information available from inside the database. Here’s a simple example of getting a directory listing:

Tutorial: Troubleshooting Linux SSH Login Delay - Why does logging in always take 10 seconds?

As I’m delivering my Linux Troubleshooting training in a couple of months, I am going to blog about some typical issues and techniques we’ll troubleshoot in the class too.
I’ll start from a relatively simple problem - logging in to a server via SSH always takes 10 seconds. The delay seems to be pretty constant, there don’t seem to be major network problems and the server is not overloaded. Yet, remote logins always take 10 seconds.

Tutorial: Troubleshooting Linux SSH Login Delay - Why does logging in always take 10 seconds?

As I’m delivering my Linux Troubleshooting training in a couple of months, I am going to blog about some typical issues and techniques we’ll troubleshoot in the class too.
I’ll start from a relatively simple problem - logging in to a server via SSH always takes 10 seconds. The delay seems to be pretty constant, there don’t seem to be major network problems and the server is not overloaded. Yet, remote logins always take 10 seconds.

Tutorial: Troubleshooting Linux SSH Login Delay - Why does logging in always take 10 seconds?

As I’m delivering my Linux Troubleshooting training in a couple of months, I am going to blog about some typical issues and techniques we’ll troubleshoot in the class too.
I’ll start from a relatively simple problem - logging in to a server via SSH always takes 10 seconds. The delay seems to be pretty constant, there don’t seem to be major network problems and the server is not overloaded. Yet, remote logins always take 10 seconds.

Tutorial: Troubleshooting Linux SSH Login Delay - Why does logging in always take 10 seconds?

As I’m delivering my Linux Troubleshooting training in a couple of months, I am going to blog about some typical issues and techniques we’ll troubleshoot in the class too.
I’ll start from a relatively simple problem - logging in to a server via SSH always takes 10 seconds. The delay seems to be pretty constant, there don’t seem to be major network problems and the server is not overloaded. Yet, remote logins always take 10 seconds.

Oracle Security Training in London with Oracle University

I have just agreed some training dates with Oracle University in London and I will be teaching my very popular two day class How to Perform a security audit of an Oracle database on the 29th and 30th April 2019....[Read More]

Posted by Pete On 07/03/19 At 12:15 PM

Connections with a wallet – redux

Wow…it is nearly 4 years ago now that I wrote an article on connecting to the database via a wallet to avoid having to hard code passwords into script. That article is here:

https://connor-mcdonald.com/2015/09/21/connection-shortcuts-with-a-wallet/

So I went to do a similar exercise on my new 18c Windows database today, and to my surprise things went pear shaped at the very first step

Oracle 19c Data Guard sandbox created by DBCA -createDuplicateDB

Here are the commands I use to create a sandbox on Linux with a CDB1 database in a Data Guard configuration. I use the latest (19c) DBCA features to create the Primary and duplicate to the Standby.

I’m doing all in a VM which is a Compute Instance provisioned in the Oracle Cloud. In this example, I have an Oracle Linux 7.6 VM.DenseIO2.24 shape with 320GB RAM and 24 cores but remember that you will not be able to scale up/down so choose according to your credits...

I have 40GB in the / filesystem

OS and filesystem installation

I’ve installed the prerequisites as root (preinstall package, sudo and HugePages — here 200GB out of the 314GB I have):

19c Observe-Only Data Guard FSFO: no split-brain risk in manual failover

Fast-Start Failover (FSFO) is an amazing feature of Oracle Data Guard Broker which brings High Availability (HA)features in addition to the Disaster Recovery (DR) one.

Data Guard as an HA solution

By default, a physical standby database protects from Disaster Recovery (like when your Data Center is on fire or underwater, or with a power cut,…). But it requires a manual action to do the failover. Then, even if the failover is quick (seconds to minutes) and there’s no loss of data (if in SYNC), it cannot be considered as HA because of the manual decision which can take hours. The idea of the manual decision is to understand the cause as it may be better to just wait in case of a transient failure. Especially if the standby site is less powerful and application performance will be degraded.