DB2 FOR LUW / DB2FORLUW / B10 - DB2

The DB2 query optimizer can use a faster method, called greedy
join enumeration, for determining the order in which to join the
tables referenced in the query when the query contains many join
operations. This APAR is only applicable when using greedy join
enumeration. If the statement was compiled with query
optimization levels 0, 1, or 2, or if you received a SQL0437W
warning with reason code 1 or reason code 2, then the query was
compiled using greedy join enumeration. Additionally if you have
the DB2_REDUCED_OPTIMIZATION registry variable set, then we can
choose to use greedy join enumeration under certain
circumstances.

When a query contains many tables with transitive joins, and
those tables are a mix of column and row-organized tables, the
greedy join enumeration might choose a non-optimal access plan;
wherein the row-organized tables are joined too early before all
the column organized tables are joined, resulting in the loss of
benefit from the BLU acceleration technology.

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If you are using a low optimization level, you can try
increasing it to a value larger than 2.  Alternatively, you can
request the appropriate join order using an optimization
profile.

not known / see Local fix

forerunner  : IT14078 
follow-up : 

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

31.05.2017
01.06.2017
01.06.2017