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

 
 Home
 E-mail Us
 Oracle Articles


 Oracle Training
 Oracle Tips

 Oracle Forum
 Class Catalog


 Remote DBA
 Oracle Tuning
 Emergency 911
 RAC Support
 Apps Support
 Analysis
 Design
 Implementation
 Oracle Support


 SQL Tuning
 Security

 Oracle UNIX
 Oracle Linux
 Monitoring
 Remote s
upport
 Remote plans
 Remote
services
 Application Server

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

 Remote S
upport  
 Development  

 Implementation


 Consulting Staff
 Consulting Prices
 Help Wanted!

 


 Oracle Posters
 Oracle Books

 Oracle Scripts
 Ion
 Excel-DB  

Don Burleson Blog 


 

 

 


 

 

 

 

 

Oracle Index-organized table (IOT) vs. Cluster table


Expert Oracle Tips by Don Burleson

 

I'm often asked "when should I use an Oracle index-organized table (IOT) vs. a single-table cluster?".  Both index-organized tables (IOTs) and cluster tables are used to reduce I/O (consistent gets and physical reads) by making the SQL more efficient.  The SQL becomes more efficient on an Oracle index-organized table (IOT) and a cluster table because less access is required to get all of the data to satisfy the request.  Another approach is Oracle Row Re-sequencing, to perform this manually.

Also see: Super App to use Oracle Index-Organized Tables (IOT's)

There are fundamental differences in the table internal structure of an index-organized table (IOT) and a single-table cluster table, and you need to understand how your table is being accessed:

  • IOT - Oracle index-organized tables - Oracle index-organized tables remove the primary key from the table and keep them solely in the index, saving disk space.  Primarily used with high-updates tables, Oracle index-organized table (IOT) structures reduce table fragmentation.  Dr. Tim Hall, author of the book "Oracle Job Scheduling" has a great discussion of Oracle index-organized table (IOT) benefits:
     
    • Accessing data via the primary key is quicker as the key and the data reside in the same structure. There is no need to read an index then read the table data in a separate structure.
       
    • Lack of duplication of the key columns in an index and table mean the total storage requirements are reduced.
       
  • Single table clusters - A single-table index cluster table is a method whereby Oracle guarantees row sequence where clustering_factor in dba_indexes always approximates blocks in dba_tables.  Hashing is used to enforce key-order, and can greatly reduce I/O if your SQL commonly does multi-block index range scans.  See this link for more information on Oracle cluster tables.  However, single table clusters require maintenance when the overflow area is used.

Alternatives to Oracle index-organized tables (IOT's)

Oracle offers several other alternatives to Oracle index-organized tables:


 

 

��  
 
 
 
 

 
 
 

 
 
Oracle performance tuning software 
 
oracle dba poster
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 -  2014

All rights reserved by Burleson

Oracle is the registered trademark of Oracle Corporation.