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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

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

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

Insanity: doing the same thing over and over again and expecting different results. – Albert Einstein In part 1 we looked at the result cache for PL/SQL Code We can also use this same technique when our function depends on tables (or views). Let’s create a simple table, add some data and a simple, slow function: CREATE OR REPLACE FUNCTION… Continue Reading →

11g, 12c, All Things Oracle Full Articles, Database Development, Oracle Database, PL/SQL

First, solve the problem. Then, write the code. – John Johnson We are always looking for ways to do things faster. Sure you can use more CPU power or more memory in the database server, but there’s a limit to that approach. Be it the amount of money being spent, the limits of the [current] CPU power or other limits…. Continue Reading →

11g, 12c, All Things Oracle Full Articles, Database Development, Oracle Database, PL/SQL

Admit that your own private Mount Everest exists. That is half the battle. – Hugh Macleod Other options In the example we used pretty much the minimum number of parameters to make it work. There are more parameters and options available. For example UPDATE_CHECK. This does pretty much the same as WITH UPDATE CHECK in views. If you insert or… Continue Reading →

10g, 11g, 12c, 8i, 9i, All Things Oracle Full Articles, Database Development, Oracle Database, PL/SQL

Views When working with views you have several options to hide some of the data. In the article on views I have told you about the way to hide columns from the table. By adding a predicate (where clause) to the view, you can restrict the rows a user sees. This would imply creating different views for different (groups of)… Continue Reading →

10g, 11g, 12c, 8i, 9i, All Things Oracle Full Articles, Database Development, Oracle Database, PL/SQL

We have been having performance problems on our test Exadata for several months. I have opened five Oracle service requests for multiple symptoms. While the cpu utilization was fairly low, Oracle background processes would hang, the OEM 12c agent would hang, backup jobs would hang, we would experience slow communications between RAC nodes, half of the cpus would be in… Continue Reading →

11g, Database Administration, Oracle Database, RAC, Troubleshooting

Views

Patrick Barel on 05 June 2013 with 1 comments

Success always occurs in private and failure in full public view. – Unknown When working with views you have several options to hide some of the data. Of course there is the possibility not to select certain columns of data in the view. This way, the user of the view doesn’t even have to know this column even exists. You… Continue Reading →

10g, 11g, 12c, 8i, 9i, All Things Oracle Full Articles, Oracle Database, PL/SQL