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Oracle Database 11gR2 Performance Tuning Cookbook

You're reading from   Oracle Database 11gR2 Performance Tuning Cookbook Shifting your Oracle Database into top gear takes a lot of know-how and fine-tuning ability. The 80+ recipes in this Cookbook will give you those skills along with the ability to troubleshoot if things starts running slowly.

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Product type Paperback
Published in Jan 2012
Publisher Packt
ISBN-13 9781849682602
Length 542 pages
Edition 1st Edition
Languages
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Author (1):
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Ciro Fiorillo Ciro Fiorillo
Author Profile Icon Ciro Fiorillo
Ciro Fiorillo
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Table of Contents (21) Chapters Close

Oracle Database 11gR2 Performance Tuning Cookbook
Credits
About the Author
Acknowledgement
About the Reviewers
www.PacktPub.com
Preface
1. Starting with Performance Tuning FREE CHAPTER 2. Optimizing Application Design 3. Optimizing Storage Structures 4. Optimizing SQL Code 5. Optimizing Sort Operations 6. Optimizing PL/SQL Code 7. Improving the Oracle Optimizer 8. Other Optimizations 9. Tuning Memory 10. Tuning I/O 11. Tuning Contention Dynamic Performance Views A Summary of Oracle Packages Used for Performance Tuning Index

Avoiding row migration


When we update a row and it does not fit entirely within the original database block due to the corresponding growth in size, we have a row migration. In the original place (where the row was stored) we have placed a pointer to the new location of the row.

How to do it...

In this recipe, we will see how to detect row migration issues, and how to avoid migrating rows in our tables. Follow these steps:

  1. Connect to HR schema:

    CONNECT hr@TESTDB/hr
    
  2. Create the table BIG_ROWS:

    CREATE TABLE HR.BIG_ROWS (
      id number NOT NULL,
      field1 char(2000) DEFAULT 'A' NOT NULL,
      field2 char(2000),
      field3 char(2000),
      field4 char(1000),
      constraint PK_BIG_ROWS primary key (ID))
    TABLESPACE EXAMPLE PCTFREE 10;
    
  3. Populate the table:

    INSERT INTO HR.BIG_ROWS (id)
    select rownum from all_objects where rownum < 101;
    
  4. Analyze the table to refresh the statistics:

    ANALYZE TABLE HR.BIG_ROWS COMPUTE STATISTICS;
    
  5. Verify if there are migrated rows:

    SELECT CHAIN_CNT FROM ALL_TABLES
    WHERE OWNER = ‹HR...
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