OCP-1Z0-052-V8.02-23题

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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

Answer: A

如图：Oracle存储模型，逻辑结构在左，物理结构在右。

逻辑结构由大到小

database-->tablespace-->segment-->extent-->oracle data block

1、数据库是由多个表空间组成。

sys@TEST0910> desc dba_tablespaces

此数据库共有7个表空间。

SQL> select tablespace_name,status,contents,segment_space_management from dba_tablespaces;

TABLESPACE_NAME STATUS CONTENTS SEGMEN

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

SYSTEM ONLINE PERMANENT MANUAL

SYSAUX ONLINE PERMANENT AUTO

UNDOTBS1 ONLINE UNDO MANUAL

TEMP ONLINE TEMPORARY MANUAL

USERS ONLINE PERMANENT AUTO

EXAMPLE ONLINE PERMANENT AUTO

TESTTBS ONLINE PERMANENT AUTO

7 rows selected.

2、每个表空间只属于一个数据库，包含一个或多个数据文件，每个数据文件只属于一个表空间。

sys@TEST0910> desc dba_data_files

sys@TEST0910> select file_id,file_name,tablespace_name,bytes/1024/1024 m,blocks from dba_data_files;

FILE_ID FILE_NAME TABLESPACE_NAME M BLOCKS

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

4 /u01/app/oracle/oradata/test0910/users01.dbf USERS 5 640

3 /u01/app/oracle/oradata/test0910/undotbs01.dbf UNDOTBS1 100 12800

2 /u01/app/oracle/oradata/test0910/sysaux01.dbf SYSAUX 660 84480

1 /u01/app/oracle/oradata/test0910/system01.dbf SYSTEM 730 93440

5 /u01/app/oracle/oradata/test0910/example01.dbf EXAMPLE 345.625 44240

6 /u01/app/oracle/oradata/test0910/testtb.dbf TESTTBS 50 6400

6 rows selected.

3、每个段包括一个或多个extents区

sys@TEST0910> desc dba_segments;

sys@TEST0910> select tablespace_name,segment_name,segment_type,extents from dba_segments where owner='SCOTT';

TABLESPACE_NAME SEGMENT_NA SEGMENT_TYPE EXTENTS

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

USERS PK_EMP INDEX 1

USERS PK_DEPT INDEX 1

USERS EMP1 TABLE 1

USERS SALGRADE TABLE 1

USERS EMP TABLE 1

USERS DEPT TABLE 1

6 rows selected.

包括:表段、表分区段、索引段、索引分区段、临时段、撤销段、BLOB、CLOB

sys@TEST0910> select distinct segment_type from dba_segments;

SEGMENT_TYPE

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

LOBINDEX

INDEX PARTITION

TABLE SUBPARTITION

ROLLBACK

TABLE PARTITION

NESTED TABLE

LOB PARTITION

LOBSEGMENT

INDEX

TABLE

TYPE2 UNDO

SEGMENT_TYPE

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

CLUSTER

12 rows selected.

4、extent，区，由相邻的数据块的组成。

sys@TEST0910> select TABLESPACE_NAME,SEGMENT_NAME,SEGMENT_TYPE,EXTENT_ID,FILE_ID,BLOCK_ID from dba_extents where owner='SCOTT';

TABLESPACE_NAME SEGMENT_NAME SEGMENT_TYPE EXTENT_ID FILE_ID BLOCK_ID

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

USERS DEPT TABLE 0 4 128

USERS PK_DEPT INDEX 0 4 136

USERS EMP TABLE 0 4 144

USERS PK_EMP INDEX 0 4 152

USERS SALGRADE TABLE 0 4 160

USERS EMP1 TABLE 0 4 528

6 rows selected.

5、块BLOCK:是数据库中最小的I/O单元,db_block_size

sys@TEST0910> show parameter db_block_size

NAME TYPE VALUE

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

db_block_size integer 8192