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70. You configured the Flash Recovery Area (FRA) for your database. The database instance is running
in ARCHIVELOG mode. The default location for the archived redo log files is the Flash Recovery Area.
Which two files are removed automatically if the space is required in the FRA as per the retention policy?
(Choose two.)
A.flashback log files
B.backups that have become obsolete
C.copies of the data files and control files
D.archived redo log files that have multiple copies in a different archive location and not backed up
Answer: AB
答案解析：
参考：http://docs.oracle.com/cd/E11882_01/server.112/e10897/backrest.htm#ADMQS12218
分配给快速恢复区的磁盘空间量取决于数据库的大小和活动级别。通常情况下，快速恢复
区越大，就越有用。理想情况下，快速恢复区应足够大，可存放数据文件和控制文件副本，
以及基于保留策略从保留的备份恢复数据库所需的闪回日志、联机重做日志和归档日志。
（简而言之，快速恢复区至少应为数据库大小的两倍，以便可保留一个备份和若干归档
日志。）
快速恢复区的空间管理由备份保留策略控制。保留策略确定文件何时过时，即何时这些文
件对达到数据恢复目标已不再有用。Oracle DB 通过删除不再需要的文件自动管理该存储。
About the Backup Retention Policy and the Fast Recovery Area
Space management in the fast recovery area is governed by a backup retention policy. A retention policy determines when files are obsolete, meaning that they are no longer needed to meet your data recovery objectives.
Retention policies can be based on redundancy of backups or on a recovery window (period of time). When using a policy based on redundancy, the fast recovery area considers a backup of a file obsolete only when the RMAN repository has records of a specified number of more recent backups of that file. When using a recovery policy based on a period of time (or window), you specify a time interval in days. Files are obsolete only when they are no longer needed for complete recovery or point-in-time recovery to a system change number (SCN) within the window. Therefore, a recovery retention policy based on a window is recommended.
Even after files in the fast recovery area are obsolete, they are typically not deleted until space is needed for new files. If space permits, files recently moved to tape remain on disk to avoid restoring them from tape for a recovery. The automatic deletion of obsolete files and files moved to tape from the fast recovery area makes it a convenient archiving destination. Other destinations require manual deletion of logs.
Select Enable Flashback Database.
This option specifies that the database should generate flashback logs in the fast recovery area, enabling you to use Flashback Database. During usual operation, the database occasionally logs images of data blocks to the flashback logs. The database automatically creates, deletes, and resizes flashback logs.
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