Database Administration & Monitoring

What is more efficient: arrays or single column values?

In PostgreSQL ( as well as in other rdbms ) you can define columns as arrays. What I wondered is: What is more efficient when it comes to space: Creating several columns or just creating once column as array? The(…)

SQL Interpolation with psql

The PostgreSQL psql utility provides some really nice features. One of these features is SQL interpolation which allows us to do interesting things, e.g. reading files and analyze the results directly in the database. This post(…)

A free PostgreSQL cloud database?

Recently I was looking for a free PostgreSQL cloud database service for testing. Why? Because I’d like to use such a cloud instance for testing no matter on which workstation or OS I am currently on. Another reason is, that(…)

PostgreSQL portable?

What a surprise: Headed over to the sourceforge page, downloaded, installed (which is just a matter of next/next/next) : Not really the latest patchset but far more than I(…)

Get the main information from Windows Server with PowerShell

This blog will present you a way to retrieve Windows Server main information via PowerShell. The goal is to be able to automate the extraction of information for different purposes: audit, report generation, dashboards…   Disclaimer: I am not a(…)

Flashback logging overhead: ‘db file sequential read’ on UNDO tablespace

By Franck Pachot . in my previous post I’ve reproduced an issue where some bulk insert into a GTT was generating too much undo. But the real case I encountered was worse: the insert was reading lot of(…)

Oracle: an unexpected lock behavior with rollback

By Franck Pachot . Here is an odd Oracle behavior I observed when a transaction that acquired a lock is rolled back. Note that this is related to a specific combination of locks that should not be encountered in(…)

Oracle 12.1.0.2: Wait event histograms in μs

By Franck Pachot . When an Oracle Database spends a high percentage of its DB time in User I/O, I usually check the wait event histograms in order to see if the storage system is working well. But today,(…)

Linux: how to monitor the nproc limit

By Franck Pachot . You probably know about ‘nproc’ limits in Linux which are set in /etc/limits.conf and checked with ‘ulimit -u’. But do you know how to handle the monitoring and be alerted when you’re close the fixed(…)

Oracle Exadata – poor optimization for FIRST_ROWS

By Franck Pachot . In a previous blog, I discussed the difference between rownum and row_number(), in particular their behaviour in implicitely adding a first_rows(n) to the optimizer. That reminded me that I forgot to blog about an(…)