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Performance Degradation Due to Row Chaining on Compressed Table (Doc ID 1204203.1)

Last updated on FEBRUARY 20, 2019

Applies to:

Oracle Database - Enterprise Edition - Version 11.2.0.1.0 and later
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Information in this document applies to any platform.

Symptoms


When table compression or tablespace compression are used, row chaining occurs after an update.  However, when the same table is not compressed and resides in a non compressed tablespace row chaining does not occur.  This appears to be affecting performance.

SQL> select table_name, tablespace_name, compression, compress_for from user_tables where table_name = 'COMP_TEST';

TABLE_NAME              TABLESPACE_NAME            COMPRESS COMPRESS_FOR
----------------------- -------------------------- -------- ------------
COMP_TEST               COMPRESS_TBS               ENABLED  OLTP

After update:

SQL> select count(*) from test_chained_rows;

  COUNT(*)
----------
   1762368


When the same table is used without compression:

select table_name, tablespace_name, compression, compress_for from user_tables where table_name = 'COMP_TEST';

TABLE_NAME              TABLESPACE_NAME                COMPRESS COMPRESS_FOR
----------------------- ------------------------------ --------  ------------
COMP_TEST               NOCOMPRESS_TBS                 DISABLED


SQL> select count(*) from test_chained_rows;

  COUNT(*)
----------
         0

Changes

 

Cause

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In this Document
Symptoms
Changes
Cause
Solution
References


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