Oracle Database - How To Unset DB_FILE_MULTIBLOCK_READ_COUNT to Default Value

Question: DB_FILE_MULTIBLOCK_READ_COUNT is set to 16 in the spfile. How to unset the parameter as it keeps reverting back to the default value?

The documentation states: “As of Oracle Database 10g release 2, the default value of this parameter is a value that corresponds to the maximum I/O size that can be performed efficiently. This value is platform-dependent and is 1MB for most platforms. Because the parameter is expressed in blocks, it will be set to a value that is equal to the maximum I/O size that can be performed efficiently divided by the standard block size.”

It is not possible to totally “unset” the DB_FILE_MULTIBLOCK_READ_COUNT parameter. If we unset the parameter, it will always show the default value. For example:

SQL> show parameter db_fil%

NAME                                  TYPE         VALUE
------------------------------------  -----------  -------
db_file_multiblock_read_count         integer      16

SQL alter system reset db_file_multiblock_read_count scope=spfile sid='*';
System altered.
SQL> shutdown immediate;
SQL> startup;

Now since the parameter is unset the default value is taken (values shown are platform dependent):

SQL> show parameter db_fil%

NAME TYPE VALUE
------------------------------------ ----------- -------
db_file_multiblock_read_count integer 8