Call now: 252-767-6166  
Oracle Training Oracle Support Development Oracle Apps

 E-mail Us
 Oracle Articles
New Oracle Articles

 Oracle Training
 Oracle Tips

 Oracle Forum
 Class Catalog

 Remote DBA
 Oracle Tuning
 Emergency 911
 RAC Support
 Apps Support
 Oracle Support

 SQL Tuning

 Oracle UNIX
 Oracle Linux
 Remote s
 Remote plans
 Application Server

 Oracle Forms
 Oracle Portal
 App Upgrades
 SQL Server
 Oracle Concepts
 Software Support

 Remote S


 Consulting Staff
 Consulting Prices
 Help Wanted!


 Oracle Posters
 Oracle Books

 Oracle Scripts

Don Burleson Blog 








Inside Oracle execution plans

Oracle Database Tips by Donald Burleson

For complete details on tuning SQL with execution plans (explain plan), see my book "Oracle Tuning: The Definitive Reference".  Also see my notes on tuning historical SQL from STATSPACK and AWR.

The "explain plan" utility is provided by Oracle to allow you to see the internal machinations of how your SQL is executed. 

For any specific SQL query you can see SQL execution plan.  In SQL*Plus you can issue the "set autotrace" command and then issue your SQL statement:

SQL> set autotrace traceonly explain
SQL> select ename from emp where empno = 22;

Execution Plan

To see the output of an explain plan, you must first create a ?plan table.? Oracle provides a script in $ORACLE_HOME/rdbms/admin called utlxplan.sql. Execute utlxplan.sql and create a public synonym for the plan_table:

sqlplus > @utlxplan
Table created.

sqlplus > create public synonym plan_table for sys.plan_table;
Synonym created.

Warning! - Explain plan gives wrong details!

It's possible that the standard relational ?explain plan for? syntax show a plan that is incorrect, and you may not see the execution plan that is actually being implemented. 
This commonly happens when your query has a bind variable.  This happens because the explain plan utility does not consider the value of a host variable, while the Oracle optimizer may consider a host variable (when bind variable peeking is enabled with the 11g adaptive cursor sharing feature.
As a remedy, you should always use the dbms_xplan utility and avoid using the Oracle implementation of the ANSI standard ?explain plan for querylist? syntax..


Global tuning with explain plans

My plan9i and plan10g scripts are invaluable for holistic SQL tuning because they examine v$sql_plan and dba_hist_sql_plan and plot summary execution plans, identifying possible unnecessary large-table full-table scans (that may result from a missing index), and many, many other techniques.

See my other notes on reading SQL execution plan here:


Get the Complete
Oracle SQL Tuning Information 

The landmark book "Advanced Oracle SQL Tuning  The Definitive Reference"  is filled with valuable information on Oracle SQL Tuning. This book includes scripts and tools to hypercharge Oracle 11g performance and you can buy it for 30% off directly from the publisher.



Oracle Training at Sea
oracle dba poster

Follow us on Twitter 
Oracle performance tuning software 
Oracle Linux poster


Burleson is the American Team

Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

Verify experience! Anyone considering using the services of an Oracle support expert should independently investigate their credentials and experience, and not rely on advertisements and self-proclaimed expertise. All legitimate Oracle experts publish their Oracle qualifications.

Errata?  Oracle technology is changing and we strive to update our BC Oracle support information.  If you find an error or have a suggestion for improving our content, we would appreciate your feedback.  Just  e-mail:  

and include the URL for the page.


Burleson Consulting

The Oracle of Database Support

Oracle Performance Tuning

Remote DBA Services


Copyright © 1996 -  2020

All rights reserved by Burleson

Oracle ® is the registered trademark of Oracle Corporation.