Re: db_file_multiblock_read_count value

daniloa_at_bbirger.intnet.mu (danilo) wrote in news:9713eeb.0210310426.17a11a7 @posting.google.com:

> Hi,
> I would like to know why we can't set Oracle parameter
> db_file_multiblock_read_count greater than 128 on a Sun system running
> Solaris 8 (with latest patches) and Oracle 9i release 2.
>
> On the OS side, we set the max. physical I/O size(maxphys) to 8 M in
> /etc/system and sd_max_xfer_size is also set to 8M in the
> /kernel/drv/sd.conf. We tried to set db_file_multiblock_read_count
> to 1024 as recommended by VERITAS (maxphys/Oracle_block_size) = 8
> M/8 K but Oracle just seems to retain the 128 value.

You have to be very careful when you set the db_file_multiblock_read_count to such a high value. The optimizer may start to favor table scans over indexes so you may not want it this high anyway.

-- 
Pablo Sanchez, High-Performance Database Engineering
http://www.hpdbe.com