Archive for the ‘Execution Plans’ Category
Wednesday, January 2nd, 2008
I've been working on a few test cases and I'm in search of some real-world data. If your production Oracle database uses system statistics, either Workload Statistics or Noworkload Statistics, and you are willing to share them, please post a comment with the output from the following two ...
Posted in 10gR2, 11gR1, Execution Plans, Optimizer, Oracle, Performance, SQL Tuning, Statistics | 29 Comments »
Wednesday, December 5th, 2007
Since the introduction of the Cost Based Optimizer (CBO) in Oracle 7.0, people have been both fascinated and terrified by it and the statistics that feed it. There has long been a belief that a degree in witchcraft or black magic is required to successfully work with the CBO. ...
Posted in Execution Plans, Optimizer, Oracle, Performance, Statistics, Troubleshooting | 8 Comments »
Wednesday, November 21st, 2007
One of the most common performance issues DBAs encounter are bad execution plans. Many try to resolve bad executions plans by setting optimizer related parameters or even hidden underscore parameters. Some even try to decipher a long and complex 10053 trace in hopes to find an answer. ...
Posted in Execution Plans, Optimizer, Oracle, Performance, SQL Tuning, Statistics, Troubleshooting | 23 Comments »
Monday, November 19th, 2007
Oracle OpenWorld 2007 has come and gone and from the Real-World Performance Group's perspective we'd consider it a successful one. The content of this year's presentations seems to have gone over quite well as shown by the number of hallway comments and emails we received. At least two ...
Posted in Data Warehousing, Execution Plans, Optimizer, Oracle, Performance, SQL Tuning, Statistics, VLDB | 3 Comments »
Wednesday, October 31st, 2007
In the Real-World Performance Roundtable, Part 2: The Optimizer, Schema Statistics, SQL Tuning at Oracle OpenWorld 2006, I worked an example of how the optimizer can have difficulty estimating the correct cardinality when there is data correlation. (The Zodiac example can be found on pages 46-49 of the presentation.) ...
Posted in 11gR1, Data Warehousing, Execution Plans, Optimizer, Oracle, SQL Tuning, Statistics, VLDB | 8 Comments »
Tuesday, October 23rd, 2007
The other day I was reading the 11g Database VLDB and Partitioning Guide and came across the below execution plan for a partial partition-wise join between sales and customers.
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| Id | Operation ...
Posted in Execution Plans, Optimizer, Oracle, SQL Tuning | 2 Comments »
Tuesday, October 16th, 2007
Here is some code to display the HIGH_VALUE/LOW_VALUE columns from USER_TAB_COL_STATISTICS which are stored as RAW datatypes.
[sourcecode language='sql']create or replace function display_raw (rawval raw, type varchar2)
return varchar2
is
cn number;
cv varchar2(32);
cd ...
Posted in Execution Plans, Optimizer, Oracle, Statistics, Troubleshooting | 1 Comment »
Friday, August 24th, 2007
Recently, I've been quite busy with performance projects and haven't had the spare time I would like to keep up on my blog. Now that those projects are behind me, I wanted to blog about the use of one feature that made a significant difference in performance on a ...
Posted in Data Warehousing, Execution Plans, Optimizer, Oracle, Performance, SQL Tuning | 1 Comment »