If we would like SQLPLUS to define your own environmental settings, put all the required commands in a file named login.sql. This is a special filename that SQLPLUS always looks for whenever it starts up. If it finds login.sql, it executes any commands in it as if we had entered then by hand. We can put any command in login.sql that we can use in SQLPLUS, including SQLPLUS commands and SQL statements. All of them executed before SQLPLUS gives us the SQL> prompt.
This is used in the same ways as LOGIN.sql but to establish default SQLPLUS settings for all users of a database.