053-666

You are working in an online transaction processing (OLTP) environment. You use the
FLASHBACKTABLE command to flash back the CUSTOMERS table. Before executing the FLASHBACK TABLE command, the system change number (SCN) was 663571. After flashing back the CUSTOMERS table, you realize that the table is not in the correct state. Now, you need to reverse the effects of the FLASHBACK TABLE command. Which is the fastest and the most efficient option to reverse the effects of the FLASHBACK TABLE command?
A. Restore the backup control file and open the database with RESETLOGS option.
B. Perform point-in-time recovery because flashback cannot be performed again on this table
C. Execute the FLASHBACK DATABASE statement to retrieve the CUSTOMERS table as it was at SCN 663571
D. Execute another FLASHBACK TABLE statement to retrieve the CUSTOMERS table as it was at SCN 663571

　　A,C 明显错误。 RESETLOGS 打开会丢失事物，和 FLASHBACK DATABASE 都是影响整个数据库的。
　　B 选项错误，使用基于时间点的恢复可以恢复这张表，但是操作很繁琐，并且这张表是可以再次闪回的。
　　D 正确，再次使用闪回语句，只要无 DDL，就可以再次进行闪回。
　　闪回表是基于 undo 的，闪回之后，原来的数据并未丢失，还可以继续进行闪回（不能跨越 DDL 点）