Re: LOB columns and migrated rows
- From: Tanel Põder <tanel.poder.003@xxxxxxx>
- To: "ORACLE-L" <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 3 Feb 2006 11:55:37 -0600
Multiple blocksizes are heavily used in TPC-C tests as well. They could help
getting the last bit of performance out of your system.
LOBs can also be a special case, when having fairly large LOBs, it could be
useful to store those in large blocksize tablespaces. Both for less storage
overhead reasons and that way Oracle is able to address longer LOB intems
without help of LOB index in some cases.
But for chained rows - what is the block size for original poster?
If your row size is less than your block size minus couple hundred bytes of
overhead then going to larger block size won't help to reduce chaining. You can
reduce row migration by appropriately measuring initial row size when it's
inserted and final row size when the row is mature and calculate appropriate
PCTFREE for your table from there.
But otherwise, there's no need to bother about chained/migrated rows unless
your query response time is too low due excessive LIOs *and* you see that large
% of the IOs are caused by fetching chained/migrated row pieces (can be seen
from "table fetch continued row" statistic).
Tanel.
----- Original Message -----
From: Joseph Amalraj
To: oracle-l@xxxxxxxxxxxxx
Sent: Friday, February 03, 2006 9:53 AM
Subject: Re: LOB columns and migrated rows
Mladen Gogala <gogala@xxxxxxxxxxxxx> wrote:
Multiple block sizes are normally used to plug in tablespaces from another
database,
typically from an OLTP to DW. It's much faster then export and import.
Multiple
block sizes are practically useless for anything else.
--
Mladen Gogala
http://www.mgogala.com
Had heard that using larger block sizes for index, will improve performance
as per
http://searchoracle.techtarget.com/tip/1,289483,sid41_gci1008028,00.html
Is having a larger block size set up for indexes only worthwhile.
Thanks
Joseph Amalraj
--
//www.freelists.org/webpage/oracle-l
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