19.Which three statements are true about Deferred Segment Creation in Oracle databases? 

A.It is the default behavior for tables and indexes.

B.It is supported for sys-owned tables contained in locally managed tablespaces

C.Sessions may dynamically switch back and forth from DEFERRED to IMMEDIATE segment creation.

D.Indexes inherit the DEFERRED or IMMEDIATE segment creation attribute from their parent table

E.It is supported for Index Organized Tables(IOTs) contained in locally managed tablespaces.

答案：ACD

延迟段创建不支持的表类型包括：索引组织表

用户SYS、SYSTEM、PUBLIC、OUTLN和XDB下的表不支持延迟段创建。

20.Which two Oracle database space management features require the use of locally managed Table spaces?

A.Oracle Managed Files(OMF).

B.Server-generated tablespace space alerts 

C.Online segment shrink

D.Free space management with bitmaps 

E.Automatic data file extension (AUTOEXTEND)

答案：CD

21.Which three statements are true about data block storage in an Oracle Database? 

A.An index block can contain row data

B.A data block header is of a fixed length

C.A table block must always contain row data

D.A block header contains a row directory pointing to all rows in the block.

E.Row data is stored starting at the end of the block

答案：ADE

22.Which two are true about a SQL statement using SET operators such as UNION?

A.The data type of each column returned by the second query must exactly match the data type of the corresponding column returned by the first query

B.The number, but not names, of columns must be identical for all SELECT statements in the query

C.The names and number of columns must be identical for all SELECT statements in the query D.The data type of each column returned by the second query is automatically converted to the data

type of the corresponding column returned by the first query

E.The data type group of each column returned by the second query must match the data type group of the corresponding column returned by the first query

答案：BE

23.Which two are benefits of external tables?

A.They support UPDATES which transparently updates records in the file system as if they were table

B.They can be queried while the database is in the MOUNT state like dynamic performance views C.They support DELETEs which transparently deletes records in the file system as if they were table rows

D.The results of a complex join or aggregating function or both can be unloaded to a file for transportation to another database

E.They can be queried, transformed, and joined with other tables without having to load the data first

答案：DE

外部表可以做任何的查询操作，好处是不需要加载到数据库中，但是不支持任何

的 dml操作。