Re: Myths & legends: temporay segments and redo
- From: Mladen Gogala <gogala@xxxxxxxxxxxxx>
- To: jonathan@xxxxxxxxxxxxxxxxxx
- Date: Sat, 11 Feb 2006 19:56:11 -0500
On 02/11/2006 05:27:26 PM, Jonathan Lewis wrote:
>
>
> I may have missed something, but I didn't see
> an example of temporary segments used by
> sorting generating any redo. Your example showed:
>
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
SQL> desc scott.test_redo;
Name Null? Type
----------------------------------------- --------
---------------------------- COL1
NUMBER(9)
COL2 VARCHAR2(20)
SQL>
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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