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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Db_block_size
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Maybe this rule of thumb a little outdated. First it depends on what kind of file system you run (journal or not), if your box can use direct IO, what is the block size of your file system, what is the maximum I/O size of your box, can you change it (before Solarid 2.7 max size was 64K, 2.7 and up you can configure it in /etc/system). Generally, if direct I/O is enabled, your block size should be equal file system block size. Standard file system block size is 8K but you can create file system with bigger block size like 16k and make your Oracle block size 16K. There is an article on Steve Adams site why large block size is better - for OLTP mainly because of lowering of the haight of the indexes . So it is a little more complex that it looks like. There were very good presentations on IOUG by Gaja Vaidyanatha(sucking up :-) ) about performance tuning and RAIDs where these issues were explained.
Alex Hillman
-----Original Message-----
From: guy ruth hammond [mailto:grh_at_agency.com]
Sent: Friday, June 09, 2000 12:40 PM
To: Multiple recipients of list ORACLE-L
Subject: Re: Db_block_size
Eric Fang wrote:
> > Thanks, Chris, Rachel and Guy for the answers. > Actually we don't have production database(anytime), > so I don't even have the archive log files. My > question is what's the benefits of increasing the > db_block_size, what is the limit?
As a rule of thumb, large block size are good for OLAP loads, and small block sizes are good for OLTP. The actual sizing depends on your OS block size. Oracle thinks in terms of blocks when it does I/O. Therefore, if you can get an Oracle block in an integral number of OS blocks, this is good. If you have to read an entire OS block, but Oracle only wants part of that to complete a data block, this is bad.
Cheers,
g
-- guy ruth hammond <grh_at_agency.com> | One is punished for being Technology Analysis & Consulting | weak, not for being cruel. 07879607148 http://www.agency.com | -- Baudelaire -- Author: guy ruth hammond INET: grh_at_agency.com Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing). ------_=_NextPart_001_01BFD25A.32AA5E10 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printableReceived on Fri Jun 09 2000 - 16:32:22 CDT
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<P><FONT SIZE=3D2>Maybe this rule of thumb a little outdated. First it =
depends on what kind of file system you run (journal or not), if = your box can use direct IO, what is the block size of your file system, = what is the maximum I/O size of your box, can you change it (before = Solarid 2.7 max size was 64K, 2.7 and up you can configure it in = /etc/system). Generally, if direct I/O is enabled, your block size = should be equal file system block size. Standard file system block size = is 8K but you can create file system with bigger block size like 16k = and make your Oracle block size 16K. There is an article on Steve Adams = site why large block size is better - for OLTP mainly because of = lowering of the haight of the indexes . So it is a little more complex = that it looks like. There were very good presentations on IOUG by Gaja = Vaidyanatha(sucking up :-) ) about performance tuning and RAIDs where = these issues were explained.</FONT></P>
<P><FONT SIZE=3D2>Alex Hillman</FONT>
</P>
<P><FONT SIZE=3D2>-----Original Message-----</FONT>
<BR><FONT SIZE=3D2>From: guy ruth hammond [<A =
HREF=3D"mailto:grh_at_agency.com">mailto:grh_at_agency.com</A>]</FONT>
<BR><FONT SIZE=3D2>Sent: Friday, June 09, 2000 12:40 PM</FONT>
<BR><FONT SIZE=3D2>To: Multiple recipients of list ORACLE-L</FONT>
<BR><FONT SIZE=3D2>Subject: Re: Db_block_size</FONT>
</P>
<BR>
<P><FONT SIZE=3D2>Eric Fang wrote:</FONT>
<BR><FONT SIZE=3D2>> </FONT>
<BR><FONT SIZE=3D2>> Thanks, Chris, Rachel and Guy for the =
answers.</FONT>
<BR><FONT SIZE=3D2>> Actually we don't have production =
database(anytime),</FONT>
<BR><FONT SIZE=3D2>> so I don't even have the archive log files. =
My</FONT>
<BR><FONT SIZE=3D2>> question is what's the benefits of increasing =
the</FONT>
<BR><FONT SIZE=3D2>> db_block_size, what is the limit?</FONT>
</P>
<P><FONT SIZE=3D2>As a rule of thumb, large block size are good for =
OLAP loads,</FONT>
<BR><FONT SIZE=3D2>and small block sizes are good for OLTP. The actual =
sizing</FONT>
<BR><FONT SIZE=3D2>depends on your OS block size. Oracle thinks in =
terms of</FONT>
<BR><FONT SIZE=3D2>blocks when it does I/O. Therefore, if you can get =
an Oracle</FONT>
<BR><FONT SIZE=3D2>block in an integral number of OS blocks, this is =
good. If</FONT>
<BR><FONT SIZE=3D2>you have to read an entire OS block, but Oracle only =
wants</FONT>
<BR><FONT SIZE=3D2>part of that to complete a data block, this is =
bad.</FONT>
</P>
<P><FONT SIZE=3D2>Cheers,</FONT>
</P>
<P><FONT SIZE=3D2>g</FONT>
</P>
<BR>
<BR>
<P><FONT SIZE=3D2>-- </FONT>
<BR><FONT SIZE=3D2>guy ruth hammond <grh_at_agency.com> | One is =
punished for being</FONT>
<BR><FONT SIZE=3D2>Technology Analysis & Consulting | weak, =
not for being cruel.</FONT>
<BR><FONT SIZE=3D2>07879607148 <A HREF=3D"http://www.agency.com" =
TARGET=3D"_blank">http://www.agency.com</A> = | -- Baudelaire</FONT>
<BR><FONT SIZE=3D2>-- </FONT>
<BR><FONT SIZE=3D2>Author: guy ruth hammond</FONT>
<BR><FONT SIZE=3D2> INET: grh_at_agency.com</FONT>
</P>
<P><FONT SIZE=3D2>Fat City Network Services -- (858) =
538-5051 FAX: (858) 538-5051</FONT>
<BR><FONT SIZE=3D2>San Diego, =
California -- Public Internet = access / Mailing Lists</FONT>
<BR><FONT =
SIZE=3D2>---------------------------------------------------------------= -----</FONT>
<BR><FONT SIZE=3D2>To REMOVE yourself from this mailing list, send an =
E-Mail message</FONT>
<BR><FONT SIZE=3D2>to: ListGuru_at_fatcity.com (note EXACT spelling of =
'ListGuru') and in</FONT>
<BR><FONT SIZE=3D2>the message BODY, include a line containing: UNSUB =
ORACLE-L</FONT>
<BR><FONT SIZE=3D2>(or the name of mailing list you want to be removed =
from). You may</FONT>
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