How the Archived Redo Log Deletion Policy works

Archived redo logs can be deleted automatically by the database or as a result of user-initiated RMAN commands. Note that *only* logs in the flash recovery area can be deleted automatically by the database.

You can use RMAN to create a persistent configuration that governs when archived redo logs are eligible for deletion from disk, by using the ARCHIVELOG DELETION POLICY. The archived redo log deletion policy is configured to NONE by default.

When the Archived Redo Log Deletion Policy Is ENABLED

You can use the CONFIGURE ARCHIVELOG DELETION POLICY command to specify when archived redo logs are eligible for deletion. This deletion policy applies to all archiving destinations, including the flash recovery area.

For archived redo log files in the flash recovery area, the database retains them as long as possible and automatically deletes eligible logs [only] when additional disk space is required.

You can also manually delete eligible logs from any location, whether inside or outside the flash recovery area, when you issue BACKUP ... DELETE INPUT or DELETE ARCHIVELOG.

When the Archived Redo Log Deletion Policy Is DISABLED

In this case, RMAN considers archived redo log files in the recovery area as eligible for deletion if they meet both of the following conditions:

1. The archived redo logs, whether in the flash recovery area or outside of it, have been transferred to the required remote destinations specified by LOG_ARCHIVE_DEST_n.
2. The archived redo logs have been backed up at least once to disk or SBT or the logs are obsolete according to the backup retention policy.

The backup retention policy considers logs obsolete only if the logs are not needed by a guaranteed restore point and the logs are not needed by Oracle Flashback Database.


Source: Oracle Documentation