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Automatic Evolution of SQL Plan Baselines
10 Dezember 08 05:00 | Striving for Optimal Performance
In the section Evolving SQL Plan Baselines of TOP (pages 299-300) I explain what an evolution is and how to manually do it. What I do not cover is the automatic evolution. In fact, I wrote only the following text about it: “In addition to the manual...
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Query Optimizer 11g – What’s new?
02 Dezember 08 10:01 | Striving for Optimal Performance
Today I presented at the DOAG Conference in Nuremberg. As the title of this post suggests, I talked about the query optimizer features introduced in Oracle Database 11g. This is an evolution of the paper I already presented at the UKOUG Conference in...
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DBMS_XPLAN.PREPARE_PLAN_XML_QUERY
21 November 08 12:11 | Striving for Optimal Performance
As of 11.1.0.7 in the package dbms_xplan there is a new function: FUNCTION prepare_plan_xml_query(plan_query IN VARCHAR2) RETURN VARCHAR2; Simply put, the function takes as input a query that extract information from a plan table (e.g. plan_table or v...
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Invisible Indexes and Hints
11 November 08 05:02 | Striving for Optimal Performance
In this post I would like to remove some misinformation about the utilization of hints with invisible indexes. Let’s start by providing you what two sources say about that topic: Oracle Database 11g: New Features for DBAs and Developers (by Sam R. Alapati...
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Invisible Indexes and Locks
17 Oktober 08 10:33 | Striving for Optimal Performance
Invisible indexes are useful to temporarily hide an index from the query optimizer. In this post, instead of explaining what invisible indexes are, I would like to show whether the database engine uses invisible indexes to avoid false contention caused...
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Granularity ‘APPROX_GLOBAL AND PARTITION’
03 Oktober 08 10:27 | Striving for Optimal Performance
The patchset 11.1.0.7 introduces in the package DBMS_STATS a new value for the parameter GRANULARITY. The description provided by the development team in $ORACLE_HOME/rdbms/admin/dbmsstat.sql is the following: 'APPROX_GLOBAL AND PARTITION' ...
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Bloom Filters
26 September 08 06:24 | Striving for Optimal Performance
Oracle Database, as of 10g Release 2, uses bloom filters in various situations. Unfortunately, no information about their usage is available in Oracle documentation. For this reason, I decided to write a paper to explain not only what bloom filters are...
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New Information in SQL Trace Files
21 September 08 09:34 | Striving for Optimal Performance
During some tests with patchset 11.1.0.7 (which is presently available for Linux 32-bit and 64-bit only) I noticed something new in the SQL trace files. Let’s see what is the difference if I run the following statements with and without the patchset...
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Long Parses and SQL Plan Baselines
11 September 08 11:36 | Striving for Optimal Performance
Few days ago, in the post entitled Long Parses, I pointed out that stored outlines can be used to shorten the parse time by restricting the number of execution plans considered by the query optimizer. As of Oracle Database 11g, stored outlines are deprecated...
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SQL Profiles in the Data Dictionary
19 August 08 09:40 | Striving for Optimal Performance
In the paper SQL Profiles (page 22) I described the data dictionary tables where the hints belonging to SQL profiles are stored. For example, with the following query it is possible to display the hints associate to the SQL profile named opt_estimate...
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Operation CONNECT BY WITH FILTERING
17 Juni 08 11:09 | Striving for Optimal Performance
It happened to me several times to being asked about the mysterious full table scan in CONNECT BY operations. In this post I would like to share with you some of the information I wrote about it in my book (pages 233 to 236) . The operation CONNECT BY...
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