Zoltan

Thanks for the response. I'm not sure whether this is platform related - all my 
tests were conducted on servers running on AIX. While the problem is not 
apparent on v5.x instances, it seems to affect v6.x instances at all our levels.

Like Margaret's experience back in 2012, the problem seems to relate 
specifically to the use of NOT in the WHERE clause -eg in the following 
example, only the last returns incorrect results:

tsm: XXXXX>select count(*) from nodes

  Unnamed[1]
------------
        1519

tsm: XXXXX>select count(*) from nodes where node_name in (select node_name from 
filespaces)

  Unnamed[1]
------------
        1413

tsm: XXXXX>select count(*) from nodes where not node_name in (select node_name 
from filespaces)

  Unnamed[1]
------------
           0

Regards
Neil


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