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Performance Archives - Page 8 of 10 - Blog dbi services

Grégory Steulet

MySQL versions performance comparison

By | Application integration & Middleware | 6 Comments

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 MySQL versions. You can find below some of the performance improvements applied to InnoDB these last years (non exhaustive list): MySQL 5.0 1. New compact storage format which can save up to 20% of the…

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Microsoft Team

SQL Server & memory leak: Are you sure?

By | Database management | 2 Comments

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 concerned SQL Server instance is limited to 54 GB according to the max server memory (GB) server option. However, he noticed that SQL Server used 60 GB of memory which did not correspond to the configured…

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Oracle Team

What about ALTER INDEX … SHRINK SPACE ?

By | Database management, Oracle | No Comments

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. Fragmented index I have an index created when the table had 1 million rows. Then, I deleted 90% of the rows. Here is the index state from: dbms_space.space_usage index_stats after an analyze index validate structure my index…

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Nicolas Jardot

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

By | Application integration & Middleware | 5 Comments

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 problem without changing the code – thanks to SQL Patch. The faulty statement was part of a daily job that was configured and started from the application during the night. Every night, the statement failed…

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Oracle Team

Oracle 12.1.0.2.1 Set to Join Conversion

By | Database management, Oracle | No Comments

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 used by default. And even in the latest Oracle 12c patchset 1 (aka 12.1.0.2.0) it is still not enabled. But it’s there and you can use it if you set optimizer_features_enabled to 12.1.0.2.1 (that’s not a typo!)….

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Stéphane Haby

SQL Server Perfmon does not start automatically

By | Application integration & Middleware | No Comments

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… What happened? 😉 Ok, to be sure that it was not a rights or a setting problem in my Data Collector Set, I tried with a System Data Collector Set and got the same error. I…

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Oracle Team

Oracle Exadata – poor optimization for FIRST_ROWS

By | Database Administration & Monitoring, Oracle | 3 Comments

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 issue I encountered and which concerns both approaches. It was on an Exadata: a nice full table scan with smartscan was taking a long time. And forcing to an index access – with a very bad index…

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Microsoft Team

Tempdb enhancements with SQL Server 2014

By | Application integration & Middleware | No Comments

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 tables for instance (aka hekaton tables). Since SQL Server 2005 version some improvements have been made for tempdb. Tempdb caching is one of them and allows to reduce the page allocation contention. Basically to create a…

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Oracle Team

Exploring Oracle SE & EE performance statistics with Orachrome Lighty

By | Database management, Oracle | No Comments

By Franck Pachot . At dbi services, we really like Lighty for Oracle, a tool which helps exploring performance statistics whether they originate from AWR (available only in Enterprise Edition with Diagnostic Pack option) or from Statspack (available via Standard Edition). As a matter of fact, we like it so much that we have became Orachrome Partner. If you want to try it out for yourselves, there is a free trial here. If you have…

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Microsoft Team

SQL Server 2014: SELECT INTO operators can run in parallel

By | Application integration & Middleware | No Comments

A couple of weeks ago, I had to provide some best practices in term of architecture for a “heavy writes” environment that consists in importing data from different sources into SQL Server tables. At the customer place, I was asked about interesting new SQL Server features that could be used to increase the performance speed of the data import process. Indeed, SQL Server 2014 provides an interesting enhancement of SELECT INTO statement that is often…

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