When you execute a log backup you back up all redo log entries that the database system has written since the last log backup from the log area to a data carrier. Once you have backed up the redo log entries, the database system can then overwrite them in the log area.
You can also back up the redo log entries automatically by activating automatic log backup.
Database Administration, Backing Up Log Entries
Database Studio, Backing up Log Entries
Database Manager CLI, Backing Up and Restoring Database Instances
Database Administration in CCMS, Scheduling Log Backups