BC remote Oracle DBA - Call (800) 766-1884  
Oracle Consulting Oracle Training Development

Remote DBA

Remote DBA Plans  

Remote DBA Service

Remote DBA RAC

   
Remote DBA Oracle Home
Remote DBA Oracle Training
Remote DBA SQL Tuning Consulting
Remote DBA Oracle Tuning Consulting
Remote DBA Data Warehouse Consulting
Remote DBA Oracle Project Management
Remote DBA Oracle Security Assessment
Remote DBA Unix Consulting
Burleson Books
Burleson Articles
Burleson Web Courses
Burleson Qualifications
Oracle Links
Remote DBA Oracle Monitoring
Remote DBA Support Benefits
Remote DBA Plans & Prices
Our Automation Strategy
What We Monitor
Oracle Apps Support
Print Our Brochure
Contact Us (e-mail)
Oracle Job Opportunities
Oracle Consulting Prices





   

 

 

 

Remote DBA services

Remote DBA Support

Remote DBA RAC

Remote DBA Reasons

Remote Oracle Tuning

Remote DBA Links

Oracle DBA Support

Oracle DBA Forum

Oracle Disaster

Oracle Training

Oracle Tuning

Oracle Training

 Remote DBA SQL Server

Remote MSSQL Consulting

Oracle DBA Hosting

Oracle License Negotiation

 

 


 

 

 

 

 

 

 

Optimizer Hints

Oracle Tips by Burleson Consulting

Optimizer mode hints are used to redirect the overall optimizer goal. The most common mode for SQL tuning is the rule hint, which is used when you suspect that the CBO is using a suboptimal execution plan. It should be noted that the optimizer hints only cause Oracle to apply the optimizer to the SQL, and additional hints can still be added for further tuning.

The all_rows Hint

The all_rows hint represents the cost-based approach designed to provide the best overall throughput and minimum resource consumption. The all_rows mode favors full-table scans and is not suitable for OLTP databases. When adding this hint to a rule-based database, make sure that all tables and indexes that participate in the query have statistics with the analyze command.

The rule Hint

The rule hint directs Oracle to apply rule-based optimization to the query. This hint is generally the first one to try when tuning a SQL statement where you suspect that the CBO is generating a suboptimal execution plan.

The rule hint ignores the table and index statistics and uses basic heuristics to generate an execution plan. Up until the release of Oracle8i, the rule-based optimizer often generated a faster execution plan than cost-based optimization.

The first_rows Hint

This is the cost-based approach designed to provide the best response time. Just as with the guidelines for adding the all_rows hint, make sure that all tables and indexes that participate in the query have statistics with the analyze command. The first_rows hint is useful when testing the execution plan for a database with a questionable optimizer mode such as choose. By using the first_rows hint, you can tune your SQL for what the CBO considers to be the fastest response time. Generally, all SQL running under optimizer_mode=choose should be tested with the first_rows and rule hints to see if the performance will improve.

Next, let’s look at how hints can be used improved to the efficiency of a table join.


This is an excerpt from "Oracle High-Performance SQL Tuning" by Donald K. Burleson, published by Oracle Press.


Expert Remote DBA

BC is America's oldest and largest Remote DBA Oracle support provider.  Get real Remote DBA experts, call
BC Remote DBA today.

 

 

Remote DBA Service
 

Oracle Tuning Book

 

Advance SQL Tuning Book 

BC Oracle support

Oracle books by Rampant

Oracle monitoring software

 

 

 

 

 

 

BC Remote Oracle Support

Remote DBA

Remote DBA Services

Copyright © 1996 -  2013 by Burleson. All rights reserved.

Oracle® is the registered trademark of Oracle Corporation.



Hit Counter