ALTER SYSTEM SWITCH LOGFILE and ALTER SYSTEM ARCHIVE LOG CURRENT both force a log switch.
From Oracle backup documentation:
After an online backup or inconsistent closed backup, always ensure that you have the redo necessary to recover the backup by archiving the unarchived redo logs. When the database is open, run the following SQL statement to force Oracle to switch out of the current log and archive it as well as all other unarchived logs:
ALTER SYSTEM ARCHIVE LOG CURRENT;
See example of hot baqckup script here:http://www.dba-oracle.com/concepts/hot_backup_script.htm