question no: 144
after running the configure retention policy to recovery window of 7 days command, what has been accomplished?
a. retain the data file backup for 7 days.
b. run the recover process every 7 days.
c. destroy the physical backup files every 7 days.
d. destroy the physical backup files older than 7 days.
e. retain one backup of each data file for at least 7 days.
f. keep the catalog information in the control file for 7 days.
答案是 e，
请问a，e 有什么区别吗？
解答:
如果在 7 天內還沒有新的備份，那麼即使舊的備份已超過 7 天，但仍然還是要保留的。這就是 a 與 e 的不同之處。
答案是e
a是說 db 的datafile
e是說 backup set 的datafile
retention policy 是定義backup保存的時間 所以答案是e