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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Table Fragmentation - Please Help - Urgent
Having many extents is not a bad thing. It is when the data is skewed all over extents that are scattered all over the disk. The query you sent does not address that, it just tells you how large the table is and how many extents.
In reguards to extents, there are two things to worry about.
The first is dictionary performance when using dictionary managed extents. This is reguards to quering the FET$ and UET$ table and C_TS# cluster. As for performance of the query at hand performance is almost compeletely uneffected. For locally managed extents, the problem is slightly different as a query of dba_extents cause a physical read across all the bitmaps in all the tablespaces.
The other problem is without using uniform size of extents, you will have many unusable fragments and this may cause probems of wasted space and poor performance. This also comes up when ST (space transaction) enqueue is held for periods of time to clean up these problems. This enqeue is serial and will show up greatly with dictionary managed extents and smon processing.
But the ammount of extents has no real bearing on the performance of a particular query in itself.
"Do not criticize someone until you walked a mile in their shoes, that way when you criticize them, you are a mile a way and have their shoes."
Christopher R. Spence OCP MCSE MCP A+ RAPTOR CNA
Oracle DBA
Phone: (978) 322-5744
Fax: (707) 885-2275
Fuelspot
73 Princeton Street
North, Chelmsford 01863
-----Original Message-----
Sent: Wednesday, August 08, 2001 7:11 AM
To: Multiple recipients of list ORACLE-L
SELECT
SEGMENT_NAME,
SEGMENT_TYPE,
BYTES/1024/1024 Kbytes,
EXTENTS
FROM
DBA_SEGMENTS
> Hello All,
>
> Please help in sending me a script for getting to know whether a
> table is fragmented or not? Also need to know whether I will need
> to Analyse the table for getting accurate results, and if yes how
> to do that?
>
> Thanks
>
> raja
>
>
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-- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: INET: murosa_at_inicia.es 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: Christopher Spence INET: cspence_at_FuelSpot.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).Received on Thu Aug 09 2001 - 18:54:34 CDT
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