Re: PARALLEL QUERY

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Sun, 28 Oct 2007 08:13:37 -0000
Message-ID: <02e001c8193a$716aee90$0200a8c0@Primary>

Looking back through the thread, the only information I have about the query is that it is:

  select /*+ parallel(bt,4) */ from big_table bt;

How many tables are there in your real query, and how many indexes are there available, and are any of the tables partitioned and which columns are declared not null, and how many lines is the serial execution plan that you get.

Regards

Jonathan Lewis
http://jonathanlewis.wordpress.com

Author: Cost Based Oracle: Fundamentals
http://www.jlcomp.demon.co.uk/cbo_book/ind_book.html

The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html

• Original Message ----- From: "DBA Deepak" <oracle.tutorials_at_gmail.com> To: "Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> Cc: <oracle-l_at_freelists.org> Sent: Saturday, October 27, 2007 9:16 PM Subject: Re: PARALLEL QUERY

> Hi Jonathan,
>
> Thanks again for your nice explanation. But I had a little difficulty in
> understanding the following....
>

>> think about ANY executions that might NOT do a parallel tablescan on table

> XXX and make it impossible for them to happen.
>
> Would be great if you can kindly elaborate on the above.
>
> In my original post in this thread Oracle completely ignored the parallel
> scan of the table even though the explain plan showed that it had lesser
> cost. As per your explanation I had restricted/limited Oracle optimizer
> (through hints) to follow parallel processing approach.
>
> Please excuse me for any kind of ignorance.
>
> Regards,
>
> Deepak
>

--
http://www.freelists.org/webpage/oracle-l

Received on Sun Oct 28 2007 - 03:13:37 CDT