Re: Effect of number of extents on Oracle I/O performance

Mark W. Farnham wrote,on my timestamp of 14/03/2009 10:58 AM:


2) When the extent size is very small (smaller than a multiblock read) then
in cases where a multiblock read is interrupted by the extent boundary every
time, then many small extents can be noticed. (If the extents are even a
reasonable size, then the collision interrupting a multiblock read quickly
becomes an infrequent event in a full table scan and the overhead disappears
in the noise.
Seen this in some of the tablespaces in our DW. Unexplained slowdowns of FTS. Since then I've changed them to UNIFORM with size 50M or 100M, depending on the tables kept there. No more problems. 

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Cheers
Nuno Souto
in sunny Sydney, Australia
dbvision@xxxxxxxxxxxx
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