You change the value of a parameter in a parameter file in one of the following ways:
By editing an initialization parameter file
In most cases, the new value takes effect the next time you start an instance of the database.
By issuing an ALTER SYSTEM SET ... SCOPE=SPFILE statement to update a server parameter file
By issuing an ALTER SYSTEM RESET ... SCOPE=SPFILE statement to remove a parameter from a server parameter file, causing the default value to take effect the next time you start an instance of the database.