Re: Parallel Query Option on 7.3.4

In article <71qf03$a93$1_at_news.monmouth.com>,   "Roman Gelfand" <rgelfand_at_masmid.com> wrote:
> select /*+ PARALLEL(TBL1, 5) */ fld1, fld2, fld3, fld4 from tbl1 order by
> fld5, fld6;
>
> The table tbl1 contains 5000 rows. Can anyone tell me why I am not seeing
> performance improvement using parallel query option.
>
> Thanks for your help
>
>

How many CPUs do you have? On how many disks is your data spread? Are there enough parallel query servers running? Is there enough memory? If your system has a memory or cpu bottleneck you will not see any gain by improving the IO. If you have one CPU, improvemnts may be very small. If all the data you are accessing is on the same drive it does not matter how many parallel processes will read it. In fact, it can decrease the performance because instead of sequential read the system will do scattered reads with all the overhead of seek operations. Besides, you do a sort, and that may take more time than actually reading the data from the disk.

Too many possibilities ;)

Cheers,

Kirill

-----------== Posted via Deja News, The Discussion Network ==---------- http://www.dejanews.com/ Search, Read, Discuss, or Start Your Own Received on Fri Nov 06 1998 - 18:32:56 CST