RE: Myths & legends: temporay segments and redo

And just in case there is any ambiguity, it does not matter whether the sort
operation is based on a normal permanent table or a global temporary table.
Either way this test produces the same result, indicating that there is no
redo during a sort-to-disk operation.

regards
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David Kurtz
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> -----Original Message-----
> You are right, as usual. I created a bit larger table and forced
> sort to disk. Redo size remained the same:
>
> NAME
>     VALUE
> ----------------------------------------------------------------
> ----------
> sorts (memory)
>      2741
> sorts (disk)
>         2
> sorts (rows)
>   4017884
>
> SQL> select n.name,s.value
> from v$statname n, v$mystat s
> where n.statistic#=s.statistic# and
> name = 'redo size';  2    3    4
>
> NAME
>     VALUE
> ----------------------------------------------------------------
> ----------
> redo size
>       672
>
> SQL> select count(*) from scott.test_redo;
>
>   COUNT(*)
> ----------
>    2000001
>
> Redo size was 672 before sorts that were forced by setting
> WORKAREA_SIZE_POLICY to
> "MANUAL" and setting the sort_area_size for the session to 64K.
> The LED on my
> hard disk immediately showed intense disk activity, but redo size
> remained the same.
> Had there been redo activity, it would have shown. GTT are
> obviously a very special
> case.
>
> --
> Mladen Gogala
> http://www.mgogala.com


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