Why is it that many times the optimizer does not parallelize a query on a nonpartitioned table or table space, even when SET CURRENT DEGREE = 'ANY' was specified?
 
Problem
Why is it that many times the optimizer does not parallelize a query on a nonpartitioned table or table space, even when SET CURRENT DEGREE = 'ANY' was specified?  
 
 
Solution
In the z/OS® and OS/390® environments, your DB2® query might be I/O bound. Because of assumptions by the optimizer, a query for which the access path starts with an outer table (or only table) that is nonpartitioned has a better chance of parallelizing if it is CPU bound (that is, if the optimizer deems it to be CPU bound). This is usually the case with rather complex queries or with many predicates.  

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With kind regards
Michael Dewert, Software GroupTechnical Sales DB2