Db_file_multiblock_read_count

[slimdave]

That's the default from 10g Release 2 onwards -- prior to that it is "8" regardless of platform or db_block_size. I think from 10gR2 onwards leaving it unset is the best choice.

[pranavgovind]

Thanks Tamil. Perfect answer for my question. I am thanking every one participating on this thread. This site is very useful.

Max I/O Size depends upon many factors such as volume manager (Veritas or LVM), stripe size , OS limitation etc.
Today, the effective max I/O size can be set to 1MB.

If you are using Veritas volume manager, then vol_maxio parameter tells you the size.

If you donot use LVM, then the best way to determine is from the extended trace data file (using 10046 events) at level 8.

Ex:
You change the db_file_multiblock_read_count = 512.
set events 10046 at level 8.
full table scan a big table.
Look for P3 value in the trace file.

Tamil