A file containing redo records. There are three types of redo logs: online redo logs, standby redo logs, and archived redo logs. The online redo log is a set of two or more files that records all changes made to datafiles and control files. The LGWR process records the redo records in the log. The current online redo log is the one to which LGWR is currently writing. The standby redo log is an optional location where the standby database can store the redo data received from the primary database. This redo data can be stored on the standby location using either standby redo logs or archived redo logs. The archived redo log, also known as the offline redo log, is a copy of the online redo log that has been copied to an offline destination. If the database is in ARCHIVELOG mode, the ARC process or processes copy each online redo log to one or more archive log destinations after it is filled. See also archived redo log, ARCHIVELOG mode, current online redo log, log switch, online redo log, and standby redo log