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 







Alter table move vs. shrink space commands

Oracle Database Tips by Donald BurlesonFebruary 8, 2015


Question:  What is the difference between "alter table move" and shrink space?

Answer:  There are several ways to reclaim wasted space in a table, but they work differently.  Also, see my notes on identifying tables for space reclamation.

  • Create table As Select (CTAS) - This copies the table rows into a clean area, lowering the high-water-mark, packing the rows densely (as dictated by PCTFREE) and releasing free space.
  • Online reorg - Using the dbms_redefinition package you can use parallel CTAS to reorganize tables, while the tables continue to accept updates.
  • Data pump (expdp, impdp) - Rarely used in high-speed production apps, except for backups.
  • Alter table move - The alter table xxx move command moves rows down into un-used space and adjusts the HWM but does not adjust the segments extents, and the table size remains the same.  The alter table move syntax also preserves the index and constraint definitions.
  • Alter table shrink space - Using the "alter table xxx shrink space compact" command will re-pack the rows, move down the HWM, and releases unused extents.  With standard Oracle tables, you can reclaim space with the "alter table shrink space" command:

SQL> alter table mytable enable row movement;
Table altered

SQL> alter table mytable shrink space;
Table altered

If you like Oracle tuning, you might enjoy my book "Oracle Tuning: The Definitive Reference", with 950 pages of tuning tips and scripts. 

You can buy it direct from the publisher for 30%-off and get instant access to the code depot of Oracle tuning scripts.



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.