March 2007
Intermediate to advanced
488 pages
13h 46m
English
book
OnDemand SQL Performance Analysis Simplified on DB2 for i5/OS in V5R4
by Hernando Bedoya, Jaime Gaug, James Kerl, Ser Ser NG, Jose Cardoso dos Santos
Content preview from OnDemand SQL Performance Analysis Simplified on DB2 for i5/OS in V5R4
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Chapter 2. DB2 for i5/OS performance basics 13
query because it allows the database to focus on the rows that it needs and perform a
minimal number of I/Os.
2.1.2 Encoded-vector index
To understand EVIs, you should have a basic knowledge of bitmap indexing. DB2 for i5/OS
does not create permanent bitmaps. SQL creates dynamic bitmaps temporarily for query
optimization.
The need for newer index technologies has spawned the generation of a variety of similar
solutions that can be collectively referred to as
bitmap indexes. A bitmap index is an array of
distinct values. For each value, the index stores a bitmap, where each bit represents a row in ...
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