RE: "direct path read" and "db file sequential read" used for full table scans in 11g

From: Allen, Brandon <Brandon.Allen_at_OneNeck.com>
Date: Thu, 30 Aug 2012 21:47:29 +0000
Message-ID: <A250F0C68C23514CA9F3DF63D60EE10E1A8251AA_at_onews32>

Question #3 is open again
According to the docs the answer I thought I'd found would only explain what I'm seeing if I had the parameter parallel_degree_policy=AUTO, but I just checked and it is set to MANUAL, so the parallel queries should still be using direct path reads according to the doc: http://docs.oracle.com/cd/E11882_01/server.112/e25513/initparams179.htm#REFRN10310

SQL> show parameter PARALLEL_DEGREE_POLICY

NAME                                 TYPE        VALUE


------------------------------------ ----------- ------

parallel_degree_policy               string      MANUAL

From: Allen, Brandon

I found the answer to question #3 - apparently it's a new feature called "In-Memory Parallel Execution" as documented at the links below. I'm still looking for answers on #1 and 2 though if anyone has any ideas.

From: Allen, Brandon

1. How can I force production to use the direct path reads?
2. Why is it using "db file sequential read" for a full table scan instead of "db file scattered read"?
3. I also tried setting PARALLEL to 2 on the table in question and it did force Oracle to use a parallel execution plan, but it still used "db file sequential read" instead of "direct path read" - any idea why this could be?

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http://www.freelists.org/webpage/oracle-l Received on Thu Aug 30 2012 - 16:47:29 CDT