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Home -> Community -> Mailing Lists -> Oracle-L -> RE: effect of Initial and Next exents...
Raghu,
There are differing opinions regarding multiple extents. I subscribe to the belief that multiple extents are not a bad thing. The latency between the extent reads is not a factor until the number of extents reaches ~4000. I remember reading a white paper on this topic, however I can't tell you exactly where it is off the top of my head.
If I was the dba for this database, I would be more concerned with fragmentation and size of extents than the number of extents. If you understand your data thoroughly, have fairly accurate estimates for growth and understand the application it is supporting, you can choose your extent sizes properly and won't have the problem of 4000+ extents. Uniform extent sizes are optimal to avoid fragmentation.
My choice to avoid fragmentation is the method in the white paper entitled 'How to Stop Defragmenting and Start Living'. I don't know about LMT's, haven't read up on them, but just from the discussions I've seen on the list about them, it looks like may be an implementation of this idea.
Here's another way to look at it: If you think multiple extents are bad, are you going to create a tablespace with a 6gb datafile for your 6gb 1-extent index and hope it doesn't grow? With larger databases this idea breaks down very quickly.
HTH, and list, correct me if I am wrong about LMT's. I can always blame it on the pain killers.
Lisa Koivu
Ft. Lauderdale, FL, USA
-----Original Message-----
From: Raghu Kota [SMTP:raghukota_at_hotmail.com] Sent: Wednesday, July 25, 2001 1:31 PM To: Multiple recipients of list ORACLE-LSubject: effect of Initial and Next exents...
Hi Friends
I obsered in my big database Tables and Indexes set different Initial and next extents..So How it will effect on performance?? Suppose one my big table has initial 72Mb and next 245Mb..All big indexes(6Gb) was set low Initial and next around 245Mb..Any ideas about the performance and rectification??...
TIA
Raghu.
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Author: Raghu Kota
INET: raghukota_at_hotmail.com
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