Oracle Database

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In the final part of this series I want to cover one last source of Parallel Execution Skew: Skew caused by Outer Joins. If you have Outer Joins where the majority of foreign key values is NULL, this can lead to the following symptoms: From a processing point of view for a parallel outer join, the NULL value in the foreign… Continue Reading →

10g, 11g, 12c, All Things Oracle Full Articles, Database Administration, Database Development, Oracle Database, Performance Tuning, Troubleshooting

Oracle Database 12c is designed for the cloud and introduces Multitenant Architecture with more than 500 new features. It enables customers to make more efficient use of their resources and reduce IT costs. What is Multitenant Architecture? Oracle 12c now introduces multitenant architecture featuring pluggable databases, which makes it easy to consolidate your databases on to the cloud, deliver high… Continue Reading →

12c, All Things Oracle Full Articles, Database Administration, Oracle Database

In this part of the series we will have a look at different approaches to how Parallel Execution Skew can be addressed via manual re-writes of an affected query. Let’s have a look at a couple of options. Approach 1: Mimic the new 12c skew aware feature Looking at the new 12c special skew aware distribution feature that I’ve introduced… Continue Reading →

10g, 11g, 12c, All Things Oracle Full Articles, Oracle Database, Performance Tuning, Troubleshooting

I’ve offered up “first child first, recursive descent” as a basic strategy for interpreting execution plans – but it’s not a perfect rule, and it can be easy to lose track of what’s going on even when the basic “first child first” is being obeyed. In this article we’ll be looking at a couple of examples where we will still… Continue Reading →

12c, All Things Oracle Full Articles, Database Administration, Oracle Database

Since Parallel Execution Skew is a common problem that can severely limit the scalability of Parallel Execution (see my previous article for a demonstration), Oracle has introduced a new feature in 12c that can address the problem automatically. That’s great, but unfortunately – at least in the initial 12c release – it only applies to a limited number of scenarios,… Continue Reading →

12c, All Things Oracle Full Articles, Oracle Database, Performance Tuning, Troubleshooting

In part 3 of this series we used a simple hash join to introduce the a simple guideline for reading execution plans – the “first child first, recursive descent” method. This allowed us to work out the order in which Oracle produced rowsources and (implicitly) the order in which it visited the different physical objects in the query. At the… Continue Reading →

All Things Oracle Full Articles, Oracle Database, Performance Tuning

In the first two articles in this series we listed a couple of methods for generating or retrieving execution plans and learned a few extra steps that could increase our confidence that we were using the right environment to investigate any problems we might have with a plan. In this article we’re going to become acquainted with a basic (though, as… Continue Reading →

All Things Oracle Full Articles, Oracle Database, Performance Tuning

Securing enterprise business-critical data is as important for DBAs as database tuning and data protection. Oracle provides comprehensive and powerful security controls/solutions to ensure data privacy and data security which will help with meeting regulatory compliance. Oracle supports the following security controls: Data Masking Advance Security (TDE, Data Redaction) Label security Virtual Private Database (VPD) Fine Grained Auditing (FGA) Data… Continue Reading →

12c, All Things Oracle Full Articles, Database Administration, Database Development

After providing a baseline for Parallel Execution working as expected in the introduction of this series, in this part I’ll demonstrate how things can go wrong with the work distribution. A Simple Example Of Parallel Execution Skew One common source of Parallel Execution Skew is a skewed foreign key, which means that the value distribution of the foreign key column… Continue Reading →

10g, 11g, 12c, All Things Oracle Full Articles, Oracle Database, Performance Tuning, Troubleshooting

When Oracle initially introduced the standby database concepts, the solo intention was to deliver the solutions to protect enterprise critical business data from any sort of natural and unnatural disasters. Since its innovation, Oracle has incorporated huge amount of new functionality/features and made several enhancements to ensure the standby database deliver and meet various user demands. This article is not… Continue Reading →

11g, All Things Oracle Full Articles, Database Administration