Oracle Consulting Oracle Training Oracle Support Development
Home
Catalog
Oracle Books
SQL Server Books
IT Books
Job Interview Books
eBooks
Rampant Horse Books
911 Series
Pedagogue Books

Oracle Software
image
Write for Rampant
Publish with Rampant
Rampant News
Rampant Authors
Rampant Staff
 Phone
 800-766-1884
Oracle News
Oracle Forum
Oracle Tips
Articles by our Authors
Press Releases
SQL Server Books
image
image

Oracle 11g Books

Oracle tuning

Oracle training

Oracle support

Remote Oracle

STATSPACK Viewer

Privacy Policy

 

   
  Oracle Tips by Burleson

OCP Instructors Guide for Oracle DBA Certification

Chapter 5 - Oracle Database Objects

Rollback Segments and Transaction Processing Workloads

SELECT CLASS, COUNT FROM V$WAITSTAT
SEE CODE DEPOT FOR FULL SCRIPT

Any non-zero value in the count column indicates rollback segment contention. Consider creating more rollback segments and begin analyzing rollback segment sizing specifications.

SELECT rn.Name "Rollback Segment", rs.RSSize/1024 "Size (KB)", rs.Gets "Gets", rs.waits "Waits", (rs.Waits/rs.Gets)*100 "% Waits", rs.Shrinks "# Shrinks", rs.Extends "# Extends" FROM sys.v_$RollName rn, sys.v_$RollStat rs SEE CODE DEPOT FOR FULL SCRIPT

Besides the obvious columns (waits, %waits) take a look at the number of shrinks and extends that are occurring. High numbers indicate that the specifications that control the size of the rollback segment (INITIAL, NEXT, MINEXTENTS, OPTIMAL) may need to be increased.

SELECT segment_name, bytes, extents FROM dba_segments
SEE CODE DEPOT FOR FULL SCRIPT

The simplest query of the three can also be the most helpful. The query should be run when database activity is high. Active rollback segments don’t have a chance to shrink back to their optimal settings. The query will help the DBA to determine if the rollback segments’ sizing specifications (INITIAL, NEXT, MINEXTENTS, OPTIMAL) are set sufficiently large enough. If the report shows that the rollback segments are allocating high numbers of extents, further sizing analysis is warranted.
 


The above text is an excerpt from:


OCP Instructors Guide for Oracle DBA Certification
A Study Guide to Advanced Oracle Certified Professional Database
Administration Techniques

ISBN 0-9744355-3-8

by Christopher T. Foot
 

http://www.rampant-books.com/book_2003_2_OCP_print.htm


Download your Oracle scripts now:

www.oracle-script.com

The definitive Oracle Script collection for every Oracle professional DBA

Linux Oracle commands syntax poster

ION Oracle tuning software

Oracle data dictionary reference poster



Oracle Forum

BC Oracle consulting support training

BC remote Oracle DBA   

 

   

 Copyright © 1996 -2016 by Burleson. All rights reserved.


Oracle® is the registered trademark of Oracle Corporation. SQL Server® is the registered trademark of Microsoft Corporation. 
Many of the designations used by computer vendors to distinguish their products are claimed as Trademarks