Performance Tuning

Category

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

It is often easy to forget this, but in many ways it is after we hit the execute button that the really exciting stuff starts with our code. A number of engines silently spring into action; including the optimizer. The optimizer analyses your SQL statement and decides the most efficient way to execute it based on the objects involved in… Continue Reading →

All Things Oracle Full Articles, Performance Tuning

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 small changes in the sampling, or in the data. We ended the article with a suggestion on how you could generate data for an “approximate” frequency histogram  that could be “good enough” to… Continue Reading →

All Things Oracle Full Articles, Database Administration, Database Development, Performance Tuning, Troubleshooting

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 distribution. We used an example of a simple status column in an orders table to demonstrate principles, talked about frequency histograms in particular, and highlighted a couple of problems associated with histograms. In part… Continue Reading →

All Things Oracle Full Articles, Database Administration, Database Development, Performance Tuning, Troubleshooting

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 examine the costs of creating them, and the potential they introduce for undesirable overheads, and then review their potential for giving you stability problems in your execution plans. This overview will be limited… Continue Reading →

All Things Oracle Full Articles, Database Administration, Database Development, Performance Tuning, Troubleshooting

The forest is thick with menace. The sunlight barely breaks through the leaves and is sludgy like curdled milk; the shadows of the branches look like gnarly fingers reaching to grasp at the pair of frightened small children. As they wind down the path, Hansel leaves a trail of pebbles. “It will help us find our way home,” he says… Continue Reading →

All Things Oracle Full Articles, Database Development, Performance Tuning, Troubleshooting

 Weds July 31st, 2013 Watch video To many people who build and run software, “performance” is a side-effect, an afterthought of designing and building “proper” features like buttons that book orders and reports that explain profitability. But great performance at scale doesn’t happen by accident. The first step to great performance is to remember what performance is: it is the… Continue Reading →

Application Development, Database Development, Performance Tuning, Webinar

  Watch video The video above is accompanied by the following resources: Analysing and Troubleshooting Parallel Execution presentation slides (.pdf) Further reading: Calculating Parameter Values for Parallelism Auto DOP and Concurrency Auto DOP and Queuing Parameter Settings Auto DOP and Parallel Statement Queuing Workload Management – Statement Queuing Workload Management – A Simple (but real) Example Parallel_degree_limit hierarchy – CPU,… Continue Reading →

Database Development, Oracle Database, Performance Tuning, Troubleshooting, Webinar

This video is a follow up to the webinar broadcast by Red Gate on 27th February 2012. Please leave a response and ask questions at the bottom of the page. View the presentation slides Watch video This webinar features a demonstration of Source Control for Oracle. You can find out more about this new tool here: Source Control for Oracle…. Continue Reading →

Database Administration, Performance Tuning, Troubleshooting, Webinar

Divide and conquer is what Oracle was thinking with this one. Table partitioning is about optimizing “medium selectivity queries”. The Oracle database has optimization techniques for high selectivity queries, with the use of indexes. If we need to process all data in a big table, we have to live with the fact it will take a while, but the engine… Continue Reading →

All Things Oracle Full Articles, Oracle Database, Performance Tuning