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Home -> Community -> Mailing Lists -> Oracle-L -> Re: confused about # of extents per segment performance issue
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.
>>> danamn2000_at_yahoo.com 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.
-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: dana mn INET: danamn2000_at_yahoo.com Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Tim Sawmiller INET: sawmillert_at_state.mi.us Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).Received on Tue Feb 27 2001 - 13:37:53 CST
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