Mika,

I was told by Netezza that a fix was made to resolve this issue in 5.0.10 (see SWS-52386 in 5.0.10 upgrade release notes).  However, prior to upgrading our system I rewrote the query.  The query was joining two large tables, Table A and Table B.  I broke the query into a 2-step process, by first creating a new table (Table C) from Table A and applying some of the filters from the where clause of my original qurey and distributing the new table using the same distribution key as in Table B.  This reduced the size and since the distribution column was my join key it offered co-located join.  (The reason I didn't just simply distribute on the join column in Table A to begin with, is that this particular column does cause some data skew, and is not used in any other queries).

We have upgraded, but if I were to do a similar query again without doing the 2-step process I get the following error: Not enough sort/merge buffers.