Since no redo log history exists to reproduce the
changes made since the last backup occurred, you will lose the effects of those
changes. Very few Oracle shops make this choice, because the inability to recover to
the point of failure is unacceptable??”it results in lost work.
The second and more practical way to address the issue is to archive the redo logs as
they fill. To understand archiving redo logs, you must first understand that there are
actually two types of redo logs for Oracle:
Online redo logs
The operating system files that Oracle cycles through to log the changes made to
the database
Archived redo logs
Copies of the filled online redo logs made to avoid losing redo data as the online
redo logs are overwritten
An Oracle database can run in one of two modes with respect to archiving redo logs:
NOARCHIVELOG
As the name implies, no redo logs are archived. As Oracle cycles through the
logs, the filled logs are reinitialized and overwritten, which erases the history of
the changes made to the database. This mode essentially has the disadvantage
mentioned above, where a failure could lead to unrecoverable data.
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