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 6. Custom Database Monitor Analysis 211
QQREST and QQTOTR
We included the QQREST (estimated rows selected) and QQTOTR (total rows in table)
columns to give you an idea of the selectivity of the statement. A great difference between
these two columns is a good indicator that index is a better alternative to a table scan
operation.
QQRID
A table scan operation is uniquely identified by the record ID (QQRID) value of 3000. We
include it as selection criteria in the common table expression tablescans.
QQI6
This column indicates a table scan operation with a cumulative elapsed time in
microseconds for each individual query. Since we use ...
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