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Home -> Community -> Mailing Lists -> Oracle-L -> RE: multiple extents are OK, dagnabbit!
Paul,
With LMT's. uniform extents sizes and properly place objects I think you avoid most of the situations you described. Cary's paper at hotsos.com shows that in a system with a lot of activity your disk head is never going to fulfill the request for a full tablescan in a single operation anyway because of all of the competing requests. Also it shows that the probability of in another request in fact being beneficial to your processes disk read goes up.
9 out of 10 DBA's agree, LMT's, uniform extents sizes and objects with < 1000 extents are just fine for most databases. These are always general rules and everyone's situation is different. Perhaps you want to keep everything under 100 extents for a DSS DB with few users, I would say that would be fine but to still stay with uniform LMT's as they are easier to manage.
-----Original Message-----
Sent: Friday, January 18, 2002 10:41 AM
To: Multiple recipients of list ORACLE-L
Hello,
My 2 cents:
It does make a difference to reorg, esp. when done thoughtfully, with a specific goal in mind. For example, if you have a order_log table that started with first extent 1MB and next extent 1MB, and this table has grown in size to say, 10 million rows (business is good), you would have hundreds of extents, and each of those new extents took some time to extend that would have been avoided if you had started with 100MB first and 25MB next. Indexes take a far worse performance hit. You also expose yourself to other issues (fragmentation, full table scans (yuck) run slower, table drops run slower, more extent overhead, recovery time runs slower, risk of failure increases).
Thank you,
Paul Sherman
DBA
voice - 781-501-4143 (office)
fax - 781-278-8341 (office)
email - psherman_at_elcom.com
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Author: Post, Ethan
INET: Ethan.Post_at_ps.net
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