Development & Performance

When you change the UNDO_RETENTION parameter, the LOB segment’s retention value is not modified

Below, I will try to explain, a particular case for the general error : ORA-01555 snapshot too old error.. Normally, when we have this error, we are trying to adapt the retention parameters or to tune our queries. SQL> show(…)

SQL Tuning – Mix NULL / NOT NULL Values

One of the difficulty when writing a SQL query (static SQL) is to have in the same Where Clause different conditions handling Null Values and Not Null Values for a predica. Let’s me explain you by an example : Users(…)

Recover a corrupted datafile in your DataGuard environment 11G/12C.

On a DG environment, a datafile needs to be recovered on the STANDBY site, in two situations : when is deleted or corrupted. Below, I will explain  how to recover a corrupted datafile, in order to be able to(…)

Pass summit – day 4

Optimizing Multi-Billion Row Tables in Tabular in 2018   I wanted to attend the session moderated by Marco Russo to see his approach of optimizing performance in Tabular model The first thing to understand is how the data is(…)

A SQLite extension for gawk (part II)

Welcome to part II of a three-part article on extending gawk with a SQLite binding. Part I is here. Part II is followed by(…)

An SQLite extension for gawk (part I)

Quick: what is the most used database management system on our planet ? Oracle ? Wrong. SQL server ? Wrong again ! MySQL ? You’re almost there. It’s SQLite. Surprised ? I must confess that I was too. Actually, SQLite(…)

SQL Server Tips: How many different datetime are in my column and what the delta?

Few months ago, a customer asks me for finding in a column, how many rows exist with the same date & time and the delta between them. The column default value  is based on the function(…)

SQL Server on Linux – I/O internal thoughts

Let’s start the story from the beginning with some funny testing I tried to perform with SQL Server on Linux a couple of months ago. At that time, I wanted to get some pictures of syscalls from SQL Server as(…)

How to fix your own SQL plan in Oracle ?

Method to build and fix your own SQL plans in Oracle and then you want to fix it for all next executions of the SQL by your application (thanks to SPM). In this post I show how fix a plan(…)

SP2 for SQL Server 2016 is available with new helpful DMVs

Last month (April 24, 2018), the Service Pack 2 for SQL Server 2016 was released and distributed. This Service Pack has new DMVs, already available in SQL Server 2017 RTM.