Re: File system block size and page size

marcco.lucky_at_laposte.net (Marcco) wrote in message news:<9f59e0a.0112221110.18cf0cd2_at_posting.google.com>...
> Sybrand Bakker <postbus_at_sybrandb.demon.nl> wrote in message news:<0mk62u8549n498m1aff080p3ajl6vgogeo_at_4ax.com>...
> > On 21 Dec 2001 02:41:14 -0800, marcco.lucky_at_laposte.net (Marcco)
> > wrote:
> >
> > >Frank van Bortel <fbortel_at_home.nl> wrote in message news:<3C222FDF.D2E36EA6_at_home.nl>...
> > >> Marcco wrote:
> > >> >
> > >> > Hello,
> > >> >
> > >> > I can see that my HP-UX ufs file system is configured
> > >> > to uses block size of 8k and page size of 4k.
> > >> > My db_block_size is set equal to 4k (equal to page size).
> > >> >
> > >> > How I can resize this. What relation, between db_block_size and
> > >> > page size. I want to increase this to 8k. Is this is possible?
> > >> >
> > >> > Thanks.
> > >>
> > >> Probably not without rebuilding the db; upto and including 8.1.7
> > >> (aka 8i Rel3) block sizes were fixed, and set during db creation.
> > >> As of 9 you can have different blocksizes for different tablespaces.
> > >> Hint: always mention versions...
> > >
> > >Thank you.
> > >
> > >Im using Oracle 8i (8.1.6).
> > >I have also some questions about: the relation between
> > >system block size, system page size and oracle db_block_size.
> > >Is increasing db_file_multiblock_read_count can replace
> > >db_block_size incresing knowing that my system block size
> > >is 8k and page size is 4k?
> > >
> > >Thanks
> >
> > No. Increasing db_block_size decreases the overhead in a table. It
> > also allows for bigger records, so for less chained records.
> > db_file_multiblock_read_count is the number of blocks Oracle will read
> > ahead during a full table scan. So, IMO, you are comparing apples and
> > pears.
> > On most operating systems (with the exception of Solaris)
> > db_block_size * db_file_multiblock_read_count should not exceed 64k,
> > as that is the number of bytes the O/S can read in one request.
>
> Hello,
>
> My system is HP-UX 11.0 which can go until 1024 bytes. Also, I read
> in "Oracle 8 Tuning T&T" book and many others, that increasing
> db_file_multiblock_read_count is somwhat equivalent to increasing
> db_block_size with advantage that there is no need to recreate the DB.
> So, I dont understand when you said that there is no comparison
> between
> these two parameters.
>
> Question remains: What happened if my system has 8 KB block size and
> page size is 4 KB, and I set my db_block_size equal to 16 kB or 32 KB?
>
>
> Thanks

There is a big problem that I don't understand why all books I'm seen( Oracle 8 DBA Tips&Techniques, Oracle 8 Performance Tuning T&T,
Oracle 8 High Performance Tuning, ....), all tell us that increasing DB_FILE_MULTIBLOCK_READ_COUNT is almost equivqlent to increasing DB_BLOCK_SIZE? Where are the authors of these books?

New question : if database use only "rowid" is increasing DB_FILE_MULTIBLOCK_READ_COUNT has any sense in performence tuning?

Thanks Received on Mon Jan 07 2002 - 10:43:13 CET