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Poor performance with parallelism ?

edited Mar 12, 2013 8:16PM in Database DataWarehousing (MOSC) 8 commentsAnswered
 Hello, In 11g, I parallelized 3 complex SELECT queries R1 R2 R3 with a degree = 10.

Time without parallelism:

R1: 1Hour

R2: 1hour 20min

R3: 40min

Time after parallelism (one SELECT after another):

R1: 12min

R2: 16min

R3: 5min

Time after parallelism (3 SELECT simultaneously):

R1: 1Hour 10min!

R2: 1Hour 30min!

R3: 50 min!

So poor performance if 3 SELECT  are running at the same time and with parallelism.

What solution to avoid this degradation?

My server has 10 CPU with dual core and 20 Go of RAM.

Thanks.

GD.

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