Troubleshooting

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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

Error Handling

Jan Leers on 06 December 2013 with 5 comments

Most programmers don’t like exceptions, but you should consider them as your closest friends. They are the ones that honestly say what is wrong with your program. We cannot foresee all possible problematic events, and even the best programmers write bugs. Exceptions There are three kinds of exceptions Internally defined: A system error, defined by Oracle, that occurs. Predefined: The… Continue Reading →

All Things Oracle Full Articles, Database Development, PL/SQL, Troubleshooting

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 we will review their potential for giving you stability problems in your execution plans. This overview will… Continue Reading →

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

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

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

Often in a complex enterprise Infrastructure Oracle DBAs face issues by enabling SMTP mail traffic on the databases through corporate email gateway servers. Imagine you have to provide your database applications an ability to send emails via Simple Mail Transfer Protocol (SMTP) protocol from Oracle database. On my blog I give a detail action plan to accomplish the same. My… Continue Reading →

Oracle Database, Troubleshooting

Database replay was introduced in Oracle 11g R1, and it allows you to capture workloads on a Production system and replay them in your Development or test environments while maintaining the unique characteristics of the workload. This enables the user to test a variety of system changes such as hardware/software migration, operating system/ database upgrade, patches, database config changes etc…. Continue Reading →

All Things Oracle Full Articles, Application Development, Database Administration, Database Development, Oracle Database, Troubleshooting

Watch video End-to-end metrics bridge the gap between the developer and the DBA, the Developer and Oracle, and the DBA and the application. Most applications today are n-tiers using a connection pool on the application tier, which makes them very hard to trace. With a little bit of collaboration between developers and DBAs, tracing can be turned on very easily… Continue Reading →

Application Development, Database Administration, Database Development, Troubleshooting, Webinar