Fw: merge command, pq slaves and sorting
- From: "jaromir nemec" <jaromir@xxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Sun, 17 Oct 2004 10:05:53 +0200
Hi,
> Can someone please verify...If the FTS spawns a number of slaves based on
> the degree, does each sort operation also get that number of slaves, is
> that correct?
You may simple verify the SQL statements that will be performed in parallel
by checking the explain plan. On execution time you can observe those SQL
statement and the actual deployed DOP querying V$SQLAREA joined to
V$SESSION.
Verify also that you don't deploy a default degree of paralellism (=number
of cpu * paralle_threads_per_cpu), which could be unacceptable large. This
could happen e.g. using a hint such as PARALLEL(a,) that overrides the DOP
defined in a table. This is in my experience the most frequent cause of
excessive paralellism.
If you observe a case, where the parallel query consumes more slaves that
the documented value of 2 times DOP + 1 coordinator, please provide the SQL
statement.
HTH
Jaromir D.B. Nemec
----- Original Message -----
From: "David" <thump@xxxxxxxxxxxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Thursday, October 14, 2004 6:44 PM
Subject: merge command, pq slaves and sorting
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