[askdba] Re: Need help with Interview Questions
- From: Ganesh Raja <ganesh.raja@xxxxxxxxx>
- To: askdba@xxxxxxxxxxxxx
- Date: Mon, 8 Nov 2004 14:53:34 +0000
Nisar,
Did not Understand too much from your Post .. But How does all the
things that you have talked about affect the way parallelism works ..
Parallelism is CPU Bound and not disk bound ... U dictate if you want
to Use Parallelism and then The ur Query/DML is Split across multiple
processess that works out how to fetch data from the database and
processes it.
I am disagreeing here with irfhan also when he says that Multiple
extents will give u chances of better parallelism. U can write a small
testcase with a One Extent Table and See what happens .. U will still
get Parallel Reads.
The Only thing that has some effect on performance with Multiple
Extent is the MBRC value since an Multi Block read cannot be done over
multiple extents. [ U will never encounter this has a Problem]
Apart from that i will never say that if you have 1000 Extents ur
Query is Going to Perform badly and if you have 1 Extent it will
perform any better. I need a test case from u to prove that the
otherway.
Extent has always been a Logical Grouping of Blocks and not a
Physicall Grouping.
My $0.02 and not my logic ... :)
Rgds
Ganesh
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