Archive for the ‘Statistics’ Category
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 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 »
Monday, September 17th, 2007
Many of you are aware of the Oracle 11g Database New Features and while some may be generally interested in new features, one area that I focus on is new features that yield gains in performance. Some of these features can be found in the General Server Performance section ...
Posted in 10gR2, 11gR1, Data Warehousing, Optimizer, Oracle, Performance, Statistics | 15 Comments »