Re: Does the number of extents affect the performance?

The number of extents in table does not affect the performance of full table scans as long as
the size of the extents is a multiple of the sizeof each read performed (DB_FILE_MULTIBLOCK_READ_COUNT * DB_BLOCK_SIZE) Mohamed El-Mallah
SDDPC Thomas Kyte wrote:

> >After reading several articles, I get an imprsssion that the fewer
> >extents in a table's data segment, the better the performance would
> >be. But I can't find this statement in any official document.
> >So I want to ask the experienced DBA about the relation between the
> >size of extent and the performance.
> >
>
> No, performance for a 1 extent table will be no different then a 100
> extent
> table. this (few extents = better performance) is a rumor.
>
> On many databases, you can run export with compress=y and see a
> measurable
> performance improvement in the resulting imported database. The
> serious flaw
> with using this data point as a "proof" that few extents is good
> is that you can use compress=n and achieve identical performance
> gains. The
> performance gains come not from reduction in the number of extents in
> database
> segments, but from the block packing and row fragmentation removal
> implicitly in
> any import.
Received on Tue Sep 09 1997 - 00:00:00 CDT