The backup shouldn't have the effect described - you should still see all the
servers (in each server set) doing similar amounts of work, not everything
happening in one server. (That sounds more like Stefan's suggestion of a skew
sending all the data to one server by accident, but that then suggests you've
got a very unlucky hash/hash distribution).
The parallel 48 query being more expensive than unhinted with with a table
degree of 32 sounds odd, but a parallel(N) hint enables some of the parallel
automatic policy stuff, which can do different arithmetic from the manual
stuff. Are the "small" tables also declared parallel ? If so, what degree ?
I think we need to see the plan and the query.
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
@jloracle
________________________________
From: Sandra Becker [sbecker6925@xxxxxxxxx]
Sent: 16 February 2016 21:01
To: Jonathan Lewis
Cc: oracle-l
Subject: Re: Not sure why parallel hint didn't work correctly
I did forget to mention that an RMAN backup was running and is still running.
It's a 30T data warehouse so backups take quite awhile. They have only 4
threads for the backup. They are working on a new backup solution so hopefully
we'll get that taken care of in the next 6 weeks. Could the backup play a part
in this?
