23.Note the following structures in your database server:

23.Note the following structures in your database server:

1: Extents

2: OS Blocks

3: Tablespace

4: Segments

5: Oracle Data Block

Which option has the correct arrangement of these structures from the smallest to the largest?

A.2, 5, 1, 4, 3

B.1, 2, 3, 4, 5

C.5, 2, 1, 3, 4

D.2, 1, 5, 4, 3

答案：A

解析：最小的应该是操作系统bolck，然后是oracle的block

然后是extents，然后是segments，然后是tablespace

SQL> l

1 select segment_name,tablespace_name,extents,blocks

2* from dba_segments where tablespace_name='USERS' and owner='SCOTT' and segment_type='TABLE'

SQL> /

SEGMENT_NA TABLESPACE EXTENTS BLOCKS

---------- ---------- ---------- ----------

DEPT USERS 1 8

EMP USERS 2 16

SALGRADE USERS 1 8

从这里我们可以看出users表空间包括多个segment，segment为dept的包括多个extent，dept包括1个extent

并且包括8个blocks，因此从这里可以看出来

blocks<extents<segment<tablespace