1  闪回区有足够空间,并且在 flashback retention target要求范围内,flashback log 将要被创建

2  一旦超过flashback retention target时间要求，flashback log将要被覆盖

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.