Value : 16K of 32K (* 1024)
This parameter in the init.ora is the most important. This can be done only during creation time. If you have already created the Database you cannot change this value. You will have to re-create the Database with a different size.
When you start to think about larger block sizes, remember that a 32KB undo block size can be a source of wasted I/O.
This block size is used for the SYSTEM tablespace and by default in other tablespaces.
The maximum value to which you can set the DB_BLOCK_SIZE is 16 KB on Linux x86. It is 32 KB on other platforms.
gerardnico@orcl>show parameter DB_BLOCK_SIZE
NAME TYPE VALUE
------------------------------------ ----------- ---------
db_block_size integer 8192
SELECT
*
FROM
v$parameter
WHERE
name = lower('DB_BLOCK_SIZE');