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When storing lot's of LOBs id worry
about:
* whether in-line storage is allowed
* PCTVERSION - for read consistency (LOBs do not
use rollback segments for data pages, only )
* CACHE - default is nocache, this requires always
direct reads & writes which can hit IO. But if you do cache, this could kill
your buffer cache, because LOB blocks read are placed to MRU (most recently
used) end of LRU list (at least in 8i I believe it used to be that
way).
* LOGGING - can be disabled when using NOCACHE
(direct writes). When logging is enabled with nocache, an update of data in LOB
writes whole datablock images in redologs. If chunk size is set bigger than one
block, then blocks of whole chunk are written to redo not depending on how much
of LOB data was actually inserted.
* CHUNK size - bigger chunks might be better
performance wise (especially for growing objects), but if set too big, can waste
space.
* other less important issues, like lob index
storage parameters...
So, there are lots of combinations.... For
example if you don't have hardware write cache, the LOB direct writes might
become bottleneck. And if you disable logging, you lose the ability to recover
from media failure. If you use CACHE, there used to be problems with buffer
cache. In 9i the alghoritms might have changed of course, but in 9i, there's
additional nice feature: multiple block sizes and buffer pools - you can just
keep your data in normal 8k block tablespaces, and LOBs in 16 or 32k block
tablespaces.
Tanel.
----- Original Message -----
Sent: Tuesday, July 29, 2003 1:49
AM
Subject: Re: LOB tablespace
Jared
This is not the case. I had imported a 150 Gig table
containing LONG RAW column to BLOB with simple Export /Import sometime back
last year and the only thing is that the column name given to BLOB column is
same. This is export import from 81.7.3 non -partitioned table to 8.1.7.3
partitioned table
Indy
Johal
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| [EMAIL PROTECTED]
Sent by: [EMAIL PROTECTED]
07/28/03 06:34 PM
Please respond to ORACLE-L
|
To:
Multiple recipients of list ORACLE-L
<[EMAIL PROTECTED]>
cc:
Subject: Re: LOB
tablespace |
You won't be storing LOB's, you will be storing LONG's.
Oracle
does not automatically convert LONG to LOB for you.
You will have to do
that yourself ( check on MetaLink ) after
you import the
data.
Assuming that your new database will be using LMT's (
locally
managed tablespaces ) I would think just set PCTFREE and
PCTUSED
to whatever you were using
previously.
HTH
Jared
"Ehresmann, David"
<[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
07/28/2003
03:09 PM
Please respond to ORACLE-L
To: Multiple recipients of list ORACLE-L
<[EMAIL PROTECTED]>
cc:
Subject: LOB
tablespace
I am going to import an Oracle 7 database into an Oracle
8.1.7.0.0
instance
that I am going to make. I have 31 tables of
which 11 hold LONG and/or
LONG
RAW column datatypes. What storage
clause should I put on the tablespace
to
hold the LOBs most
efficiently?
thanks,
David Ehresmann.
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