677.What are the prerequisites for performing flashback transactions? (Choose all that apply)
A.Supplemental log must be enabled
B.Supplemental log must be enabled for the primary key
C.Undo retention guarantee for the database must be configured
D.EXECUTE permission on the DBMS_FLASHBACK package must be granted to the user
Answer: ABD
答案解析：
参考：http://blog.csdn.net/rlhua/article/details/12224763
要使用闪回回退事务处理功能，必须启用补充事件记录功能并建立正确的权限。例如，HR方案中的HR用户决定对REGIONS表使用闪回事务处理。SYSDBA可确保数据库处于归档日志模式，
并在SQL*Plus 中执行以下设置步骤：
alter database add supplemental log data;
alter database add supplemental log data (primary key) columns;
grant execute on dbms_flashback to hr;
grant select any transaction to hr;
