Consider that direct path event are the ones involve
in f.e. sort_direct_writes=TRUE in 8.0.X or 7.3.X. In
8i doesn't exist as a parameter. However it is feature
included in the engine with default values for their
buffers. Also insert /*+ APPEND */ or sql*loader
direct=y generates that kind of wait. And I don't
think is bad. Although you should take a look of the
paging. Take into account that this wait doesn't use
the buffer cache.
On the other hand as you said increasing the sort area
size doesn't imply an improvement in sorts
performance. You can say it is a matter of paging.
However it is also a matter of the way Oracle resolves
sorting and the merging with the temp tablespace. As a
renmark if you can avoid all the sorting increasing
the sort area you could feel the improvement.
And in the case of the merging with temp tablespace
refer to the sort_multiblock_read_count 8i parameter
Regards.-
--- Johnson Poovathummoottil [EMAIL PROTECTED]
wrote:
We too had a similar problem and thought that we
should do something to make the sorts faster. But
investigating a little deeper found the actual
amount
of time waited in direct path read/write was very
little although there are a number waits attibuted
to
direct path read and write while sorting. We also
tried increasing the sort_area_size, but it gave
adverse performance.
Of the total time spend for the query cpu time was
always above 90 percent and wait time was less than
10
%. we executed the same queries on faster cpu
machines
and got better results. Also parallelizing the
queries
helped.
--- [EMAIL PROTECTED] wrote:
How many extents are being written to your
temporary
tablespace?
You could increase your sort_area_size if you have
the memory.
I have seen 1 gig of temp tablespace being chewed
up
reduced to 0 by tuning the sql.
You may not always realize that your program
statements invoke a sort. Sorting is performed by
the following statements:
In my case I put an index on the columns in the
order by and that took care of the sorts to disk.
w CREATE INDEXw DISTINCT
w GROUP BYw ORDER BY
w INTERSECT w MINUS
w UNION w Unindexed table joins
w Some correlated subqueries
Depending on your system, you can put your
temporary
files on a Raid 1 layout.
HTH
Mike
[EMAIL PROTECTED]
On Mon, 09 July 2001, WinterSun_Zhao wrote:
Hi, DBAs:
I find a process occupy about 50% Cpu. I
checked
the wait event, it was waiting for the event of
direct path write.
I know it is because it is writing to the
temporary tablespace. The extent size of the
temporary tablespace is 5M, it is temporary.
Would you please tell me how to improve the
performance of Direct path write? How to
decrease
its cpu occuption.
Thanks!
WinterSun Zhao
Oracle DBA ( 2 yr+)
Unix SysAdmin ( 4 yr)
[EMAIL PROTECTED]
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