Performance

When to gather workload system statistics?

By Franck Pachot . This month we started to give our Oracle Tuning Workshop. And with a new workshop comes new questions. We advise to give to the optimizer the most accurate statsistics that we can have. That(…)

Don’t forget to configure Power Management settings on Hyper-V

Recently I had the opportunity to audit a SQL Server database hosted on a Hyper-V 2012 cluster. I noticed that the guest operating system had the Power Plan configured to High performance. This is great thing but when I talked to(…)

MySQL versions performance comparison

This blog aims to make a performance comparison between the different MySQL versions/editions and also comparing the differents MySQL forks such as Percona Server and MariaDB.  Indeed number of improvements as been done to innodb storage engine in the last(…)

SQL Server & memory leak: Are you sure?

I have recently come across an issue with one of my customer that told me that their SQL Server 2008 R2 instance had a memory leak. These are strong words! The server has 64 GB of RAM and the(…)

What about ALTER INDEX … SHRINK SPACE ?

By Franck Pachot . I have recently published a script to check index fragmentation. But then, do you COALESCE or REBUILD? Well, there also is another option: ALTER INDEX SHRINK SPACE. Let’s compare all those index defragmentation operations.

SQL Patch: Another way to change the plan without changing the code

Recently, at a customer site, I faced a performance issue. However, as often the statement is embedded in the application so it’s not possible to rewrite the query. In this blog post, we’ll change the execution plan to solve the(…)

Oracle 12.1.0.2.1 Set to Join Conversion

By Franck Pachot . Recently, I described the Partial Join Evaluation transformation that appeared last year in Oracle 12c. I did it as an introduction for another transformation that appeared long time ago in 10.1.0.3 but was not(…)

SQL Server Perfmon does not start automatically

I have recently used perfmon (performance monitor) at a customer site. I created a Data Collector Set to monitor CPU, Memory, Disk, and Network during one day. Then, I ran the monitor and I received a “beautiful” error message…(…)

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(…)

Tempdb enhancements with SQL Server 2014

SQL Server 2014 is definitively designed for performance and I will try to demonstrate it during this blog post. I like to talk about hidden performance features because generally it does not require any changes for applications unlike in-memory(…)