Oracle will also look in the starting directory (where you launch SQL*Plus) for login.sql. As mentioned, you can set global login parameters in glogin.sql. When you start SQL*Plus, the environment variables that were in existence when you started stay in existence for that window. You can host out (>! UNIX command or >host UNIX command or simply >host) to do something in your shell window. However, you cannot effect a change with respect to environment variables in your SQL*Plus session.