This really depends on the type of access. If it's random using indexes, the extents
don't matter much. If you do a lot of full table scans, and the extents are scattered
all over, there may be a performance degradation. YMMV as always.
[EMAIL PROTECTED] 02/27/01 01:06PM
Apparently, it's a widely held myth that a large # of extents (let's
say "BETWEEN 5 AND 1000") per table segment is bad for performance. Yet
the same sources who label the belief mistaken persist in pushing for
fitting all of a table in the INITIAL extent.
And that confuses the heck out of me.
What gives?
Is it that fetching a new extent on the fly, the act of obtaining a new
extent, creates too much overhead? And finis, no more concern beyond
this?
If you approached a database for the first time and it already
contained a segment with 500 extents, would that segment's number of
extents not be a performance concern unless you expected it to continue
grabbing new extents? Let's say it would never have a new insert,
update, or delete. Would there be any performance value in crushing the
segment down to fit in one extent?
What's the definitive answer on this?
I remain confused about coalescing as well; anyone know of a good
whitepaper or article on coalescing/fragmentation for Oracle 8 and
beyond?
Thanks.
- Dana
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