Oracle recommends that your database block size match, or be
multiples of your operating system block size. One can use smaller
block sizes, but the performance cost is significant. Your choice should
depend on the type of application you are running. If you have many
small transactions as with OLTP, use a smaller block size. With fewer
but larger transactions, as with a DSS application, use a larger block
size. If you are using a volume manager, consider your "operating
system block size" to be 8K. This is because volume manager products
use 8K blocks (and this is not configurable).