OCP 1Z0 053 215

215.Which two statements regarding the Flashback Table feature are correct? (Choose two.) 
A. Flashback Table can be performed on system tables. 
B. Flashback Table operation does not shrink the segments. 
C. Flashback Table uses log mining to extract SQL_REDO and SQL_UNDO statements. 
D. Flashback Table operation acquires exclusive data manipulation language (DML) locks. 
Answer: BD 

对D存疑
flashback是ddl不是dml
见
http://docs.oracle.com/cd/E11882_01/server.112/e41084/statements_1001.htm#SQLRF30042

The DDL statements are:

ALTER ... (All statements beginning with ALTER, except ALTER SESSION and ALTER SYSTEM—see "Session Control Statements" and "System Control Statement")
ANALYZE
ASSOCIATE STATISTICS
AUDIT
COMMENT
CREATE ... (All statements beginning with CREATE)
DISASSOCIATE STATISTICS
DROP ... (All statements beginning with DROP)
FLASHBACK ... (All statements beginning with FLASHBACK)
GRANT
NOAUDIT
PURGE
RENAME
REVOKE
TRUNCATE

http://docs.oracle.com/cd/E11882_01/backup.112/e10642/rcmflash.htm#BRADV89743

Prerequisites of Flashback Table

To use the Flashback Table feature on one or more tables, use the FLASHBACK TABLE SQL statement with a target time or SCN.

You must have the following privileges to use the Flashback Table feature:

• You must have been granted the FLASHBACK ANY TABLE system privilege or you must have the FLASHBACK object privilege on the table.

• You must have SELECT, INSERT, DELETE, and ALTER privileges on the table.

• To flash back a table to a restore point, you must have the SELECT ANY DICTIONARY or FLASHBACK ANY TABLE system privilege or the SELECT_CATALOG_ROLErole.

For an object to be eligible to be flashed back, the following prerequisites must be met:

• The object must not be included the following categories: tables that are part of a cluster, materialized views, Advanced Queuing (AQ) tables, static data dictionary tables, system tables, remote tables, object tables, nested tables, or individual table partitions or subpartitions.

• The structure of the table must not have been changed between the current time and the target flash back time.

  The following DDL operations change the structure of a table: upgrading, moving, or truncating a table; adding a constraint to a table, adding a table to a cluster; modifying or dropping a column; adding, dropping, merging, splitting, coalescing, or truncating a partition or subpartition (except adding a range partition).

• Row movement must be enabled on the table, which indicates that rowids will change after the flashback occurs.

  This restriction exists because if rowids before the flashback were stored by the application, then there is no guarantee that the rowids correspond to the same rows after the flashback. If your application depends on rowids, then you cannot use Flashback Table.

• The undo data in the undo tablespace must extend far enough back in time to satisfy the flashback target time or SCN.

  The point to which you can perform Flashback Table is determined by the undo retention period, which is the minimal time for which undo data is kept before being recycled, and tablespace characteristics. The undo data contains information about data blocks before they were changed. The flashback operation uses undo to re-create the original data.

  To ensure that the undo information is retained for Flashback Table operations, Oracle suggests setting the UNDO_RETENTION parameter to 86400 seconds (24 hours) or greater for the undo tablespace