15. 01. 2020.

Primary Key and duplicate rows – fast troubleshooting

Recently I had a case of duplicate rows in a table with Primary Key enabled. More common case is to catch CBO (Cost Based Optimizer) to return a wrong results, mainly due to sophisticated nature of CBO engine (CBO is the most complex part of the Oracle database), the complex SQLs you issue, and the […]

14. 01. 2020.

Oracle Multiversion Read Consistency and its impact on ETL

Imagine you need to create an ETL workflow that uses the Oracle database as one of its sources or even more common situation where you need to synchronize local table with table from the remote Oracle database via dblink. The most common scenario is to apply the following steps: I have a local table for […]

13. 01. 2020.

Descending Index type – performance and limitations

The main topic of this article is the DESC index type, which is often mixed-up with the Btree index type because of the great similarity they share when looking at the index creation syntax. “Raison d’etre” for having DESC index type is to avoid expensive sorting when you are sure you’ll always query and sort […]

10. 01. 2020.

Case for using unusable index

I work with Oracle more than I can remember, but every day I find something new. This time I’m asked to drop one index on the production system, which is the simplest task you can get, right? I new there had to be a problem with that, otherwise someone else would do it. In any […]

07. 01. 2020.

Oracle database links – performance impact

In this post I’m going to explain the most important drawbacks when using db links technology for purposes for which it is not design for. To be more precise, the case in which db links are used to massively exchange data between many separate databases will be explained. In the previous post you can find […]

02. 01. 2020.

Oracle database links – locking strategy

In this post mechanism of Oracle database link technology along with locking strategy used by Oracle database will be described. Today in almost all production environments based on Oracle databases where I’ve been called to help with optimization & tuning, it is a quite common to have at least one or more db links to […]

16. 12. 2019.

Oracle RAC in the AWS Cloud – performance testing part III

This is the last part of the series called “Oracle RAC in the AWS Cloud”. In my previous article I’ve promised to put a Oracle RAC cluster under the crazy load. It was time to fulfill my promise. My previous articles you can find on the following two links: https://www.performatune.com/en/oracle-rac-in-the-aws-cloud-performance-testing-part-i/ & https://www.performatune.com/en/oracle-rac-in-the-aws-cloud-performance-testing-part-ii/ Let’s go straight […]

09. 12. 2019.

Oracle RAC in the AWS Cloud – performance testing part II

In the 2nd part of the Oracle RAC in the AWS Cloud series I’ll present test results of Oracle 2 nodes RAC databases running on AWS public cloud based on Flashgrid’s Skycluster deployment. You can take a look at my previous article that are related to how to deploy & setup environment for Oracle RAC […]

03. 12. 2019.

Oracle RAC in the AWS Cloud – performance testing part I

Last time, all components (network, storage, Grid infrastructure…) are prepared for Oracle database RAC installation with a minimal time and effort thanks to Flashgrid’s wizard which, behind the scene, is using Cloud Formation template to setup everything, including installation of all necessary patches available at the time of installation.   You can find more on […]

23. 11. 2019.

Flashgrid Skycluster – Oracle RAC in the Cloud – review

Recently I’ve completed review of the FlashGrid Skycluster, an Oracle RAC deployed (in this particular test) on AWS Public Cloud IaaS, although Azure and GCP are also supported.   Flashgrid specializes for Oracle RAC, either on-premises or in the Cloud, where all three major Cloud providers are supported. When you ask yourself what is so […]