Oracle Database lets you save filled groups of redo log files to one or more offline destinations, known collectively as the archived redo log. The process of turning redo log files into archived redo log files is called archiving. This process is only possible if the database is running in
ARCHIVELOG mode. You can choose automatic or manual archiving.
An archived redo log file is a copy of one of the filled members of a redo log group. It includes the redo entries and the unique log sequence number of the identical member of the redo log group. For example, if you are multiplexing your redo log, and if group 1 contains identical member files
b_log1, then the archiver process (ARCn) will archive one of these member files. Should
a_log1 become corrupted, then ARCn can still archive the identical
b_log1. The archived redo log contains a copy of every group created since you enabled archiving.
When the database is running in
ARCHIVELOG mode, the log writer process (LGWR) cannot reuse and hence overwrite a redo log group until it has been archived. The background process ARCn automates archiving operations when automatic archiving is enabled. The database starts multiple archiver processes as needed to ensure that the archiving of filled redo logs does not fall behind.
You can use archived redo logs to:
Recover a database
Update a standby database
Get information about the history of a database using the LogMiner utility
See Also:The following sources document the uses for archived redo logs: