August 2012
Intermediate to advanced
452 pages
15h 41m
English
book
Optimizing DB2 Queries with IBM DB2 Analytics Accelerator for z/OS
by Paolo Bruni, Patric Becker, Willie Favero, Ravikumar Kalyanasundaram, Andrew Keenan, Steffen Knoll, Nin Lei, Cristian Molaro, P S Prem
Content preview from Optimizing DB2 Queries with IBM DB2 Analytics Accelerator for z/OS
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Chapter 10. Query acceleration management 231
With DB2 Analytics Accelerator, the REASON column on DSN_STATEMNT_TABLE
serves a dual purpose. In addition to listing the reason why DB2 used default values to
estimate the cost, the PROFILEID text is also appended to its value.
If DB2 has enough information to estimate the cost (that is, without using default values)
then the column REASON in DSN_STATEMNT_TABLE shows only the PROFILEID
string concatenated with the PROFILEID value whenever a qualifying profile is used for
that query.
For example, EXPLAIN populates the REASON column with the value PROFILEID 1,
which means that PROFILEID number 1 was ...
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