Use SPFILE to reset the configured initialization parameters to the default values of the system.

Use SPFILE to reset the configured initialization parameters to the default values of the system.
Start with SPFILE. If you want to restore the initialization parameter to the default value, use a statement like this:
Alter system reset db_create_file_dest;
This statement modifies entries in the SPFILE. The error message after the two parameters reset statement is executed in the experiment can also be verified.
1. Change Parameters
BYS @ bys1> show parameter db_create_file
NAME TYPE VALUE
-----------------------------------------------------------------------------
Db_create_file_dest string
BYS @ bys1> alter system set db_create_file_dest = '/home/Oracle /';
System altered.
View changes
BYS @ bys1> show parameter db_create_file
NAME TYPE VALUE
-----------------------------------------------------------------------------
Db_create_file_dest string/home/oracle/

2. Restore the changed parameters to the default values.
BYS @ bys1> alter system reset db_create_file_dest;
System altered.
In the current instance, the parameter is changed and is not reset to the system default value.
--- You need to restart the database to re-apply the parameters in SPFILE to display the default system parameters for resetting.
BYS @ bys1> show parameter db_create_file
NAME TYPE VALUE
-----------------------------------------------------------------------------
Db_create_file_dest string/home/oracle/

The second time you run the reset parameter command, the error prompt also verifies that the reset parameter command modifies the statements in SPFILE.
BYS @ bys1> alter system reset db_create_file_dest;
Alter system reset db_create_file_dest
*
ERROR at line 1:
ORA-32010: cannot find entry to delete in SPFILE

3. Restart the database and verify that the modified parameters have been restored to the system default.
BYS @ bys1> conn/as sysdba
Connected.
SYS @ bys1> shutdown immediate ;.
SYS @ bys1> startup
SYS @ bys1> show parameter db_create_file
NAME TYPE VALUE
-----------------------------------------------------------------------------
Db_create_file_dest string

Another SPFILE setting error causes the database to fail to start.

SPFILE error causing database startup failure (ORA-01565)

Oracle SPFILE damaged during online modification

Oracle modifies the SPFILE file path

Basic management of Oracle 10g RAC SPFILE

New Features of Oracle 11g-instructions for managing SPFILE