706. You execute the following command to set the redundancy retention policy in Recovery Manager
(RMAN):
RMAN> CONFIGURE RETENTION POLICY TO REDUNDANCY 3;
Identify the statement that correctly describes the implications of this command.
A, when there are already three backups, for the fourth backup RMAN removes the oldest backup.
B. When there are already three backups, for the fourth backup RMAN marks the oldest backup as
obsolete.
C. the number of backups that are retained is equ al to three and it includes full, incremental, and
cumulative backups.
D. when there are already three backup, one of the existing backups must be removed manually before
taking the fourth backup.
Answer: A
答案解析：
参考：http://docs.oracle.com/cd/E11882_01/backup.112/e10642/rcmconfb.htm#BRADV89436
个人觉得应该选B,超过冗余度的备份，rman会标志为obsolete，除非使用DELETE OBSOLETE来删除。
Configuring a Redundancy-Based Retention Policy
The REDUNDANCY parameter of the CONFIGURE RETENTION POLICY command specifies how many full or level 0 backups
of each data file and control file that RMAN should keep. If the number of full or level 0 backups for a specific data file or control file exceeds the REDUNDANCY setting, then RMAN considers the extra backups
as obsolete. The default retention policy is REDUNDANCY 1.
As you produce more backups, RMAN keeps track of which ones to retain and which are obsolete. RMAN retains all archived logs and incremental backups that are needed to recover the nonobsolete backups.
Assume that you make a full backup of data file 7 on Monday, Tuesday, Wednesday, and Thursday. You now have four full backups of this data file. IfREDUNDANCY is 2, then the Monday and Tuesday backups
are obsolete. If you make another backup on Friday, then the Wednesday backup of data file 7 becomes obsolete.
Assume a different case in which REDUNDANCY is 1. You run a level 0 database backup at noon on Monday, a level 1 cumulative backup at noon on Tuesday and Wednesday, and a level 0 backup at noon on Thursday.
Immediately after each daily backup you run the command DELETE OBSOLETE. The Wednesday DELETEcommand
does not remove the Tuesday level 1 backup because this backup is not redundant: the Tuesday level 1 backup could be used to recover the Monday level 0 backup to a time between noon on Tuesday and noon on Wednesday. However, the DELETE command
on Thursday removes the previous level 0 and level 1 backups.
Run the CONFIGURE RETENTION POLICY command at the RMAN prompt, as in the following example: