Re: LOB questions

Any 'large' object is tricky, and ones at the small end of the scale are a major pain
because they can waste so much size.

Extreme example: assume you have a 3K
LOB size - if you store this in line, then you waste about 1K per 4K oracle block, and
virtually any table access will be one block per row. Store it out of line with a chunk size of 4K (one oracle block) and you still waste 1K per block in the lob segment, but you get better I/O hit rates on non-LOB
data.

Alternatively if you have a 16K block size, then you could get 5 whole LOBS in the
block with virtually no wastage. Since the minimum CHUNK size is one block, an
out of line LOB would take 16K with 12K
wastage.

--

Jonathan Lewis
Yet another Oracle-related web site:  http://www.jlcomp.demon.co.uk

Yong Huang wrote in message <8q8p0j$409$1_at_news.sinet.slb.com>...


>I'm interested in this. How does the second question depend on block size?

 I


>assume you mean Oracle block, not OS block size? Since this is something

>new, I can't find much info on the Internet. I read Mike Ault's fairly

>well-known paper "Going out for the LOB". It doesn't help,

 performance-wise.


>

>Thank you.

>

>Yong Huang

>yhuang_at_indigopool.com

>

>Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk> wrote in message

>news:969398533.29498.0.nnrp-04.9e984b29_at_news.demon.co.uk...

>> [snipped]

>> The second question depends on your block

>> size and the LOB CHUNK size.  Be careful

>> of setting a large CHUNK size when you

>> expect to handle only small LOBs.

>> --

>>

>> Jonathan Lewis

>> Yet another Oracle-related web site:  http://www.jlcomp.demon.co.uk

>>

>> fly13_at_my-deja.com wrote in message <8q7sj8$iss$1_at_nnrp1.deja.com>...

>> >Hi all,

>> >

>> >I have few questions about LOB storing.

>> >-The first one is : If i am in DISABLE STORAGE IN ROW mode, is the a

>> >storage location busy if there is no LOB data for the row.

>> >-The second one : if i have LOB which size is about 4k, does the

>> >performance will be very much better if i use this DISABLE STORAGE IN

>> >ROW mode than storing data in-line.

>> >

>> >Cheers

>> >

>> >Fly13

>> >

>> >

>> >Sent via Deja.com http://www.deja.com/

>> >Before you buy.

>>

>>

>

>