OCP-1Z0-053-V13.02-686题

686. You execute the following FLASHBACK TABLE command:

 

Which two statements are correct?(Choose two.)

A.The EMP table that was dropped by  mistake earlier is restored.

B.The FLASHBACK TABLE statement is  executed as a single transaction.

C.The FLASHBACK TABLE statement does not maintain existing indexes on the EMP table.

D.The changes made to the EMP table since the specified time are undone if no constraint is violated during flashback.  

Answer: AD 

答案解析：

排除法：A错，C错，D正确

正确选BD

A，应该使用FLASHBACK TABLE ... TO BEFORE DROP来恢复，利用回收站原理。A错

参考：http://docs.oracle.com/cd/E11882_01/backup.112/e10642/rcmflash.htm#BRADV89742

• Logical Flashback Features Useful in Backup and Recovery

  The remaining flashback features operate at the logical level. The logical features documented in this chapter are as follows:

  • Flashback Table

    You can recover a table or set of tables to a specified point in time in the past without taking any part of the database offline. In many cases, Flashback Table eliminates the need to perform more complicated point-in-time recovery operations. Flashback Table restores tables while automatically maintaining associated attributes such as current indexes C错, triggers and constraints, and not requiring you to find and restore application-specific properties.

    "Rewinding a Table with Flashback Table" explains how to use this feature.

  • Flashback Drop

    You can reverse the effects of a DROP TABLE statement.

    "Rewinding a DROP TABLE Operation with Flashback Drop" explains how to use this feature.

    
    
    
    

参考：http://docs.oracle.com/cd/E11882_01/server.112/e25494/tables.htm#ADMIN01505

Recovering Tables Using Oracle Flashback Table

Oracle Flashback Table enables you to restore a table to its state as of a previous point in time. It provides a fast, online solution for recovering a table that has been accidentally modified or deleted by a user or application. In many cases, Oracle Flashback Table eliminates the need for you to perform more complicated point-in-time recovery operations.

Oracle Flashback Table:

• Restores all data in a specified table to a previous point in time described by a timestamp or SCN.

• Performs the restore operation online.

• Automatically maintains all of the table attributes, such as indexes, triggers, and constraints that are necessary for an application to function with the flashed-back table.

• Maintains any remote state in a distributed environment. For example, all of the table modifications required by replication if a replicated table is flashed back.

• Maintains data integrity as specified by constraints. Tables are flashed back provided none of the table constraints are violated. D正确

  This includes any referential integrity constraints specified between a table included in the FLASHBACK TABLE statement and another table that is not included in theFLASHBACK TABLE statement.

• Even after a flashback operation, the data in the original table is not lost. You can later revert to the original state.

  
  

  
  

  参考：http://docs.oracle.com/cd/E11882_01/backup.112/e10642/rcmflash.htm#BRADV81517