Krijan

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New Playground and Cheatsheet for Learning Python

I'm learning Python and I decided to create a repository where I could put Python script samples with standard Python syntax, structures and …

Python Programming

Understanding Parallel Execution - Part 1

<i>by Randolf Geist</i><p><b>Maximizing the performance of the Parallel Execution feature in Oracle Database Enterprise Edition</b><p>November 2012<p>Read Part 1 <br>Read Part 2<p>…

Basics of the Cost Based Optimizer – Part 1 - Simple Talk

This series on Oracle’s Cost Based Optimizer is aimed at the less experienced DBAs and developers to help them understand what the optimizer is …

Basics of the Cost Based Optimizer – Part 2 - Simple Talk

In the first installment of this series I gave an informal description of how the optimizer would consider the possibilities when choosing an …

Basics of the Cost Based Optimizer – Part 3 - Simple Talk

In the second installment of this series we looked at individual access paths for the tables in a simple join query to highlight an important flaw in …

Basics of the Cost Based Optimizer – Part 4

In the first three installments of this series I outlined the mechanisms used by Oracle to analyze a very simple query. Sticking with the informal …

Execution Plans Part 11: Actuals - Simple Talk

So far in this series we’ve talked about interpreting the shape of an execution plan and understanding the meaning of the predictions that the …

Execution Plans Part 10: Guesswork - Simple Talk

In part 9 we saw an example of a simple nested loop join where the basic method for interpreting the numbers in an execution plan started to break …

Execution Plans Part 8: Cost, time, etc. - Simple Talk

It’s time to move away from the <i>shape</i> of an execution plan and turn our attention to some of the numerical information we get from the plan. In this …

Execution Plans Part 9: Multiplication - Simple Talk

In part 8 we looked at a very simple execution plan involving a hash join; but that example was too simple to give us the full flavour of the …

Execution Plans Part 7: Query Blocks and Inline Views - Simple Talk

When we examine an execution plan, we’re usually trying to work out the mechanical steps that Oracle took to produce a result set. When we do this, …

Execution Plans Part 6: Pushed Subqueries - Simple Talk

In part 5 of this series we examined a couple of examples where you had to handle the <i>“first child first”</i> rule with a little care. In part 6 we …

Execution Plans part 5: First Child Variations - Simple Talk

I’ve offered up <i>“first child first, recursive descent”</i> as a basic strategy for interpreting execution plans – but it’s not a perfect rule, and it can …

Execution Plans Part 4: Precision and Timing - Simple Talk

In part 3 of this series we used a simple hash join to introduce the a simple guideline for reading execution plans – the <i>“first child first,</i> …

Execution Plans Part 3: “The Rule” - Simple Talk

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 …

Execution Plans Part 2: Things to see - Simple Talk

In part 1 of this series we saw two basic ways of creating, or acquiring, execution plans. The first method gave us the optimizer’s prediction of …

Execution Plans: Part 1 Finding plans - Simple Talk

If you have to tackle performance problems in an Oracle database one of the most important skills you need to acquire is the ability to interpret …

Histograms Part 1 – Why? - Simple Talk

In this short series on histograms we will be looking at the reasons why we need histograms and the methods Oracle has to create them. We will …

Histograms Part 3 – When? - Simple Talk

In part 2 we looked at the way that Oracle collects and uses height –balanced histograms, and raised the problem of how sensitive they could be to …

Histograms Part 2 - Simple Talk

In part 1 of this series we discussed the reasons why we might want to create some histograms to help the optimizer deal with skewed data …

Exadata

Inevitably there’s still excitement and uncertainty in the air about Exadata – and/or the Database Machine. For ease of reference and a jolly good …

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Solid Choices for Oracle Tuning on Solid State Disk

As I continue to work on very large databases, (VLDB), I am exposed to more opportunities to speed up IO. This can involve Oracle’s solution of …

How Oracle Locking Works

<b>Myth: Oracle has a Central Locking System</b><p>A week or so ago I started a new series – 100 Things You Probably didn’t Know about Oracle Database . Part 1 …

100 Things You Probably Didn't Know About Oracle Database

Recently, while delivering a presentation on Cache Fusion at New York Oracle Users Group (www.nyoug.org), the regional user group where I have been a …