PGA and SORT_AREA_SIZE

Question

Hi,
I have one sql query with sort operation (select * from table order by col1,col2,col3,col4) and I have measured the pga,uga and direct temp statistics of this session (from other session).
When I set up SORT_AREA_SIZE to be very large (about 1GB) and workarea_size_policy to 'MANUAL' I have expected that all sort will be done entirely in memory because my table is not large to much (about 40000 rows), so I expected:
physical reads direct temporary tablespace = 0
physical writes direct temporary tablespace = 0
1) It is true when I am testing on 10.1.0.4.0 oracle database (Linux 2.6.9-55.0.0.0.2.ELsmp i686)
2) When I am testing on 10.2.0.4.0 database (Linux 2.6.18-53.el5 x86_64) I get output like this:
physical reads direct temporary tablespace 2377
physical writes direct temporary tablespace 2377
I asked myself how it is possible to see this physical reads/writes (because I have already executed my sort operation, before, so this is soft parse and I have setup the SORT_AREA_SIZE to be 1GB).
Best regards,
Dragan

Answer 1

There were some bugs related to setting session parameters (don't remember what versions affected). Try to repeat your test case, but with double executing each ALTER SESSION, i.e.
alter session set sort_area_size=1073741824;
alter session set sort_area_size=1073741824;
alter session set workarea_size_policy=manual;
alter session set workarea_size_policy=manual;