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 









Cache Oracle DUAL - table caching

Don Burleson


Many Oracle databases have high consistent gets (and hence, high CPU consumption) from excessive "select 1 from dual; calls. 

This issue is fixed in Oracle10g with the new "fast dual" execution plan, but you can do a trick in earlier releases of Oracle to reduce consistent gets (logical I/O) from three to zero.

There are two ways to cache the dual fixed table in Oracle; this, take your pic:

Fix approach One:

connect sys/mypass as sysdba;
create view x_$dual as select * from x$dual ;

grant select on x_$dual to public;

connect my_schema_owner/mypassword; 

create synonym DUAL for sys.x_$dual ;

Fix approach Two:

1. Allocate a small keep pool if it doesn't exist.

2. From the sys user issue "alter table dual cache storage(buffer_pool keep);

3. This will drop the consistent gets from accessing dual from 3 to 0.

4. The problem is dual is always an FTS so it is placed at the end of the LRU and is aged out fast. By marking it as cached and placing it in the Keep pool this is avoided. In order to get to 0 CR  I had to use both cache and the keep option to make this work.

This caching of the dual fixed table can greatly reduce CPU consumptions of certain applications.



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.