About the Flashback Database Window【每日一译】--20121118

The range of SCNs for which there is currently enough flashback log data to support
the FLASHBACK DATABASE command is called the flashback database window. If
space in the flash recovery area is low, then flashback logs may be deleted to free space
for files required by the configured retention policy. The result is that the flashback
database window can be shorter than the flashback retention target, depending upon
the size of the flash recovery area, other backups that must be retained and how much

flashback logging data is needed.

对于SCN的范围，当前存在有足够的闪回日志去支持闪回数据库命令，它叫作闪回数据库窗口。

如果空间在闪回区太少了，那么闪回日志应该删一些去释放一些需要的空间通过配置时期策略。

结果就是闪回数据库窗口可以比闪回时期的目标时间更短。它取决于闪回区的大小，其它的备

份备份被获取并且有多少闪回日志是被需要的。