RE: Db_block_size

df -k is not giving you the os block size. The -k just specifies it in 1024 blocks vs 512. In AIX try fileplace <filename> and it shows the block size and fragment size if specified. For JFS in AIX I'm not sure you can change the block size from 4K.

eg.

fileplace file.sql

File: file.sql Size: 274 bytes Vol: /dev/lv03 Blk Size: 4096 Frag Size: 4096 Nfrags: 1 Compress: no

  Logical Fragment

  0219932                            1 frags     4096 Bytes,  100.0%

• Brian
  • Sandeep Kurliye <Sandeep.Kurliye_at_almarai.com> wrote:
    >
    >
    > When you issue command 'df -k', it gives you operating system block
    > size in
    > header.
    >
    > This is an observation on AIX 4.3.2.
    >
    > Sandeep.
    >
    > -----Original Message-----
    > From: Subramaniam, Lakshmi (L.) [SMTP:lsubrama_at_ford.com]
    > Sent: Thursday, July 20, 2000 2:15 AM
    > To: Multiple recipients of list ORACLE-L
    > Subject: RE: Db_block_size
    >
    > How do we find the operating system block size on unix?
    >
    > Lakshmi
    > -----Original Message-----
    > From: Alex Hillman [mailto:alex_hillman_at_physia.com]
    > Sent: Friday, June 09, 2000 6:49 PM
    > To: Multiple recipients of list ORACLE-L
    > Subject: RE: Db_block_size
    >
    >
    >
    > Maybe this rule of thumb a little outdated.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
    > <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 <http://www.agency.com> |
    > -- Baudelaire
    > --
    > Author: guy ruth hammond
    > INET: grh_at_agency.com
    >
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    >
    > --
    > Author: Sandeep Kurliye
    > INET: Sandeep.Kurliye_at_almarai.com
    >
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