Database Administration & Monitoring

In pgSentinel: the sampling approach for PostgreSQL I mentioned that one of the advantages of the ASH approach is the ability to drill down from an overview of the database activity, down to the details where we can do some tuning. The idea is to always focus on the components which are relevant to our tuning goal:

Here is the first test I did with the beta of pgSentinel. This Active Session History sampling is a new approach to Postgres tuning. For people coming from Oracle, this is something that has made our life a lot easier to optimize database applications. Here is a quick example showing how it links together some information that are missing without this extension.

The installation of the extension is really easy (nore details on Daniel’s post):

cp pgsentinel.control /usr/pgsql-10/share/extension
cp pgsentinel--1.0.sql /usr/pgsql-10/share/extension
cp pgsentinel.so /usr/pgsql-10/lib


If you follow this blog, you should know how I like Orachrome Lighty for Oracle, for its efficiency to monitor database performance statistics. Today Orachrome released the beta version of Lighty for Postgres: https://orachrome.com/news/la-beta-de-lighty-for-postgresql-est-ouverte/
The Cloud is perfect to do short tests with more resources than my laptop, especially the predictability of performance, then I started a Bitnami Postgres Compute service on the Oracle Cloud and did some tests with pgbench and pgio.

The installation is easy:

This week I took some days off to do something related to my job but a bit different. I’ve given a course on Databases and SQL. But not for my usual customers. And not with the database I know the best. So, it is still in a domain that I know, but out of my comfort zone. And this is something that we should do more often because it gives a little apprehension and a big satisfaction.

With this trend of CQRS architectures where the transactions are streamed to a bunch of heterogenous eventually consistent polyglot-persistence microservices, logical replication and Change Data Capture becomes an important component, already at the architecture design phase. This is good for existing products vendors such as Oracle GoldenGate (which must be licensed even to use only the CDC part in the Oracle Database as Streams is going to be desupported) or Dbvisit replicate to Kafka. But also for Open Source projects.

You may wonder what I’m doing with those technologies that are completely different from what I usually do. I’ll detail in a future blog post but the idea is giving a short introduction to databases to students at https://powercoders.org/, a coding academy for refugees in Switzerland. They install MAMP (My Apache – MySQL – PHP) during their curriculum for website development, and then I’ll use this environment to teach data modeling and SQL basics. Thus, I’ve to look at MAMP, PHP and MySQL for the first time… And I decided to load the OpenFlights open data to play with.
That explains the title.

Remember the times when the Oracle Software features were the same on all platforms? Where Oracle databases could be ported to any relevant platform? Where we were able to try any feature, freely, by downloading the latest release software? Now we need to think differently. Because:

The new release of Oracle VM VirtualBox (aka VirtualBox) is there with a new functionality to export a VM to the Oracle Cloud Compute (aka Oracle Cloud Infrastructure). That can be interesting to prepare a VM on my laptop and move it to the Cloud to get it accessible from everywhere. Here’s my first try. In my opinion, it’s idea but probably need further evolution.

VirtualBox

Here is what is new: in addition to .ova you can export to an Oracle Public Cloud image:

There are little changes when you go to multitenant architecture and one of them is that you must connect with a service name. You cannot connect directly to a PDB with a beaqueath (aka local) connection. This post is about a workaround you may have in mind: create a common user and set a logon trigger to ‘set container’. I do not recommend it and you should really connect with a service. Here is an example.

Imagine that I have a user connecting with bequeath connection to a non-CDB, using user/password without a connection string, the database being determined by the ORACLE_SID. And I want to migrate to CDB without changing anything on the client connection configuration side. The best idea would be to use a service, explicitly or implicitly with TWO_TASK or LOCAL. But let’s imagine that you don’t want to change anything on the client side.

The old way to get a user dump trace file, for sql_trace (10046), Optimizer compilation trace (10053), lock trace (10704), Optimizer execution trace (10507),… is to go to the server trace directory. But if you don’t have access to the server (as in the ☁) the modern (12cR2) way is to select from V$DIAG_TRACE_FILE_CONTENTS. Before everybody is on 12.2 I’m sharing here a sqlplus script that I use for a long time to get the trace file to the client.