5.3.5.1 Rules for Retention and Deletion of Flashback Logs
The following rules govern the flash recovery area's creation, retention, overwriting and deletion of flashback logs:
A flashback log is created whenever necessary to satisfy the flashback retention target, as long as there is enough space in the flash recovery area.
A flashback log can be reused, once it is old enough that it is no longer needed to satisfy the flashback retention target.
If the database needs to create a new flashback log and the flash recovery area is full or there is no disk space, then the oldest flashback log is reused instead.
Note:
Re-using the oldest flashback log shortens the flashback database window. If enough flashback logs are reused due to a lack of disk space, the flashback retention target may not be satisfied.
If the flash recovery area is full, then an archived redo log may be automatically deleted by the flash recovery area to make space for other files. In such a case, any flashback logs that would require the use of that redo log file for the use of FLASHBACK DATABASE are also deleted.