2013年4月27日 星期六

10:38

1oracle 存储架构:

1)  database  ------------tablespace-------------segment(对象) ------------extent----------data block

tablespace------------  datafiles ----------------------------------data block

2oralce segment(段对象) 的类型

1) table segment ---------建立table时,表有记在存储数据时,记录在写入数据块时候,是 随机的无序的,访问采用全表扫描。

2) partition table--------对大的table(>2G) 进行分区,减少资源竞争,提高访问速度。

3) cluster(簇) -------------------用于优化表与表的连接查询(用于表与表之间主外键连接查询,加快读取速度)

4) index-------------------提高表的访问速度

5) index organized table(IOT) -------------用于以主键方式建立索引的表,将表中的数据和索引表的数据放在一起 提高访问速度。

 3、存储空间分配:以extent 为最小单位(extent data block 组成)

 data block

oracle 10g 标准块:8k,支持2~32k

有block header 、free space 、data 组成

数据块并发访问:由数据块的事务槽来分配

initrans :初始化事务槽的个数(1·255) ,表默认1,index 默认为2;

maxtrans: 最大的事务槽个数 (默认255)

pctfree:预留给update 操作的空间,free space 大于pctfree 可以insert,小于,不允许insert

 、数据块的free space 管理

1) 手动:在数据字典上建立free list

2) 自动:在本地管理的表空间,通过bitmap来管理data block 的free space(oracle 10g 默认,除了临时、undo表空间)

SYS @ prod >select tablespace_name,contents ,extent_management  “ext_man”,segment_space_management “seg_man”   from dba_tablespaces;

 

TABLESPACE_NAME            CONTENTS       EXT_MAN      SEG_MAN

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

SYSTEM                               PERMANENT         LOCAL      MANUAL

UNDOTBS1                               UNDO               LOCAL      MANUAL

SYSAUX                               PERMANENT          LOCAL      AUTO

TEMP                                  TEMPORARY           LOCAL      MANUAL

USERS                                 PERMANENT          LOCAL      AUTO

TEST                                    PERMANENT          LOCAL      AUTO

6、建立对象的存储信息:

SQL> create table test (id int)  tablespace users;

SQL> insert into test values (1) ;

SQL> insert into test values (2) ;

SQL> insert into test values (3) ;

SQL> commit;

SYS@ prod>desc  user_segments;

Name                                                              Null?    Type

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

SEGMENT_NAME                                                               VARCHAR2(81)

PARTITION_NAME                                                             VARCHAR2(30)

SEGMENT_TYPE                                                               VARCHAR2(18)

TABLESPACE_NAME                                                            VARCHAR2(30)

BYTES                                                                      NUMBER

BLOCKS                                                                     NUMBER

EXTENTS                                                                    NUMBER

INITIAL_EXTENT                                                             NUMBER

NEXT_EXTENT                                                                NUMBER

MIN_EXTENTS                                                                NUMBER

MAX_EXTENTS                                                                NUMBER

PCT_INCREASE                                                               NUMBER

FREELISTS                                                                  NUMBER

FREELIST_GROUPS                                                            NUMBER

BUFFER_POOL                                                                VARCHAR2(7)

SYS@ prod>select SEGMENT_NAME,SEGMENT_TYPE ,TABLESPACE_NAME,bytes/1024/1024,BLOCKS,extents ,initial_extent/1024/1024 from user_segments  where        segment_name='TEST';

SEGMENT_NAME    SEGMENT_TYPE       TABLESPACE     BYTES/1024/1024     BLOCKS    EXTENTS    INITIAL_EXTENT/1024/1024

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

TEST                         TABLE                      USERS                      .0625                       8                1                        .0625

SQL> select  TABLESPACE_NAME ,INITIAL_EXTENT/1024/1024 ,NEXT_EXTENT/1024/1024, EXTENT_MANAGEMENT from dba_tablespaces     where TABLESPACE_NAME='USERS';

TABLESPACE_NAME        INITIAL_EXTENT/1024/1024         NEXT_EXTENT/1024/1024       EXTENT_MANAGEME

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

USERS                             .0625                                                                                                   LOCAL

-----------建立对象如果没有指定存储参数,则继承tablespace 的存储参数,test表分配了一个区,大小为4m

SQL> select segment_name,segment_type,TABLESPACE_NAME,EXTENT_ID,bytes/1024/1024,blocks from user_extents  where segment_name='TEST';

SEGMENT_NAME         SEGMENT_TYPE       TABLESPACE_NAME                 EXTENT_ID     BYTES/1024/1024     BLOCKS

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

TEST                                        TABLE                            USERS                                      0                              4                        512

--------------EXTENT_ID 为extent的id号,从0 开始

SQL> select table_name, TABLESPACE_NAME ,PCT_FREE,INI_TRANS ,MAX_TRANS,NUM_ROWS,BLOCKS,EMPTY_BLOCKS from user_tables   where table_name='TEST';

TABLE_NAME                     TABLESPACE_NAME          PCT_FREE      INI_TRANS     MAX_TRANS   NUM_ROWS     BLOCKS EMPTY_BLOCKS

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

TEST                                   USERS                                    10               1                          255

SQL> analyze table test compute statistics;

Table analyzed.

----------对test 表进行分析,oracle通过分析的信息来建立计划进行优化

SQL> select table_name, TABLESPACE_NAME ,PCT_FREE,INI_TRANS ,MAX_TRANS,NUM_ROWS,BLOCKS,EMPTY_BLOCKS from user_tables

where table_name='TEST';

TABLE_NAME                     TABLESPACE_NAME            PCT_FREE       INI_TRANS     MAX_TRANS     NUM_ROWS      BLOCKS      EMPTY_BLOCKS

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

TEST                                          USERS                                   10                1                          255                       3                           54                458

---------------blocks 代表已经使用过的块,empty_blocks 代表从未使用过的块

HWM :High water Market 高水位线,在segment用来区分已经使用的块和从未使用的块(在做全表扫描时,会一直扫描到HWM)

SQL> begin

for i in 4..100000 loop

insert into test values (i) ;

end loop;

end;

/

SQL> analyze table test compute statistics;

Table analyzed.

SQL> select table_name, TABLESPACE_NAME ,PCT_FREE,INI_TRANS ,MAX_TRANS,NUM_ROWS,BLOCKS,EMPTY_BLOCKS from user_tables

where table_name='TEST';

TABLE_NAME       TABLESPACE_NAME        PCT_FREE     INI_TRANS  MAX_TRANS   NUM_ROWS     BLOCKS      EMPTY_BLOCKS

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

TEST                              USERS                                  10                 1                   255                   100000                182             330

建立autotrace ,跟踪sql语句

SQL> conn /as sysdba

Connected.

SQL> @?/rdbms/admin/catplan.sql;

创建PLUSTRACE 角色

SQL>    conn /as sysdba

SQL>   @ ?/sqlplus/admin/plustrce.sql

SQL>   grant plustrace to public

源文档 <http://www.itpub.net/forum.php?mod=viewthread&tid=1747729>

set autotrace on 打开自动跟踪

set autotrace off 关闭自动跟踪

set autotrace traceonly 只显示trace 信息,不显示对象的记录信息

------------对test 做全表扫描

SQL> set autotrace traceonly;

SQL> select * from test;

Execution Plan

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

Plan hash value: 1357081020

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

| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU) | Time     |

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

|   0 | SELECT STATEMENT  |      |   100K|   390K|    49  (15) | 00:00:01 |

|   1 |  TABLE ACCESS FULL| TEST |   100K|   390K|    49  (15) | 00:00:01 |

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

Statistics

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

1  recursive calls

0  db block gets

6851  consistent gets

0  physical reads

0  redo size

1855907  bytes sent via SQL*Net to client

73710  bytes received via SQL*Net from client

6668  SQL*Net roundtrips to/from client

0  sorts (memory)

0  sorts (disk)

100000  rows processed

SQL> delete from test;

delete from test

*

ERROR at line 1:

ORA-30036: unable to extend segment by 8 in undo tablespace 'UNDO_TBS01'

---------undo 表空间太小,不能 auto extend

SQL> /

FILE_NAME                                             FILE_ID TABLESPACE_NAME

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

/u01/app/oracle/oradata/lx02/system01.dbf                   1 SYSTEM

/u01/app/oracle/oradata/lx02/lx02.dbf                      11 LX02

/u01/app/oracle/oradata/lx02/OLTP01.DBF                     7 OLTP

/u01/app/oracle/oradata/lx02/indx01.dbf                     6 INDX

/u01/app/oracle/oradata/lx02/example01.dbf                  5 EXAMPLE

/u01/app/oracle/oradata/lx02/user01.dbf                     4 USERS

/u01/app/oracle/oradata/lx02/sysaux01.dbf                   3 SYSAUX

/u01/app/oracle/oradata/lx02/rtbs01.dbf                     2 RTBS

/u01/app/oracle/oradata/lx02/test01.dbf                     8 TEST

/u01/app/oracle/oradata/tbs16k01.dbf                        9 TBS_16K

/u01/app/oracle/oradata/lx02/lx01.dbf                      10 LX01

/u01/app/oracle/oradata/lx02/undotbs01.dbf                 12 UNDO_TBS01

/u01/app/oracle/oradata/lx02/test02.dbf                    13 TEST

/u01/app/oracle/oradata/bigtbs01.dbf                       14 BIG_TBS

SQL> alter database datafile 12 autoextend on next 10m maxsize 500m;

Database altered.

-----------undo tablespace自动扩展

SQL> delete from test;

100000 rows deleted.

SQL> set autotrace off

SQL>  select table_name, TABLESPACE_NAME ,PCT_FREE,INI_TRANS ,MAX_TRANS,NUM_ROWS,BLOCKS,EMPTY_BLOCKS from user_tables

where table_name='TEST';

TABLE_NAME                     TABLESPACE_NAME                  PCT_FREE  INI_TRANS  MAX_TRANS   NUM_ROWS     BLOCKS      EMPTY_BLOCKS

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

TEST                                                 USERS                                      10                 1                   255                    0                           182             330

----------delete       删除数据    不会重置高水位       没有释放占用的数据块

               Truncate  删除数据   并且重置高水位        释放占用的数据块】

SQL> insert into test values (1) ;

SQL> insert into test values (2) ;

SQL> commit;

SQL> set autotrace on;

SQL> select * from test;

ID

----------

1

2

Execution Plan

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

Execution Plan

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

Plan hash value: 1357081020

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

| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU) | Time     |

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

|   0 | SELECT STATEMENT  |      |     2 |    26 |     2   (0) | 00:00:01 |

|   1 |  TABLE ACCESS FULL| TEST |     2 |    26 |     2   (0) | 00:00:01 |

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

Note

-----

- dynamic sampling used for this statement

Statistics

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

28  recursive calls

0  db block gets

10  consistent gets

0  physical reads

0  redo size

451  bytes sent via SQL*Net to client

385  bytes received via SQL*Net from client

2  SQL*Net roundtrips to/from client

0  sorts (memory)

0  sorts (disk)

2  rows processed

---------delete 不释放已经使用的块,所以两行记录在做全表扫描的时候也要访问所有已经使用过的块(扫描到HWM)

SQL> set autotrace off

SQL> truncate table test;

Table truncated.

SQL> analyze table test compute statistics;

SQL>  select table_name, TABLESPACE_NAME ,PCT_FREE,INI_TRANS ,MAX_TRANS,NUM_ROWS,BLOCKS,EMPTY_BLOCKS from user_tables

where table_name='TEST';

TABLE_NAME                     TABLESPACE_NAME                  PCT_FREE  INI_TRANS  MAX_TRANS   NUM_ROWS     BLOCKS    EMPTY_BLOCKS

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

TEST                                           USERS                                          10                1                    255                       0                       0                   512

SQL> insert into test values (1) ;

SQL> insert into test values (2) ;

SQL> commit;

SQL> analyze table test compute statistics;

Table analyzed.

SQL> select table_name, TABLESPACE_NAME ,PCT_FREE,INI_TRANS ,MAX_TRANS,NUM_ROWS,BLOCKS,EMPTY_BLOCKS from user_tables

where table_name='TEST';

TABLE_NAME                     TABLESPACE_NAME                  PCT_FREE  INI_TRANS  MAX_TRANS   NUM_ROWS     BLOCKS    EMPTY_BLOCKS

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

TEST                                               USERS                                      10                 1                   255                       2                      54               458

SQL> set autotrace on

SQL> select * from test;

ID

----------

1

2

Execution Plan

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

Plan hash value: 1357081020

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

| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU) | Time     |

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

|   0 | SELECT STATEMENT  |      |     2 |     4 |     2   (0) | 00:00:01 |

|   1 |  TABLE ACCESS FULL| TEST |     2 |     4 |     2   (0) | 00:00:01 |

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

Statistics

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

1  recursive calls

0  db block gets

4  consistent gets

0  physical reads

0  redo size

451  bytes sent via SQL*Net to client

385  bytes received via SQL*Net from client

2  SQL*Net roundtrips to/from client

0  sorts (memory)

0  sorts (disk)

2  rows processed

------------【truncate操作会释放 该对象的存储空间的高水位线】

SQL> create table t01 (id int)

    pctfree 20 pctused 40 initrans 3

   storage( initial 128k next 1m pctincrease 50) ;

Table created.

SQL> select table_name,TABLESPACE_NAME,PCT_FREE,PCT_USED ,INI_TRANS,INITIAL_EXTENT/1024,NEXT_EXTENT/1024/1024,PCT_INCREASE from user_tables

where table_name='T01';

TABLE_NAME                     TABLESPACE_NAME                  PCT_FREE   PCT_USED  INI_TRANS     INITIAL_EXTENT/1024      NEXT_EXTENT/1024/1024 PCT_INCREASE

------------------------------ ------------------------------ ---------- ---------- ---------- ------------------- --------------------- --------------------------------- -----------------T01                                                 USERS                                      20                     3                 128                     4                                            0

---------在local 管理的表空间上,存储参数设置意义不大

SQL> select owner, SEGMENT_NAME,TABLESPACE_NAME, BYTES   from dba_segments

where owner='SCOTT';

OWNER                          SEGMENT_NAME         TABLESPACE_NAME                     BYTES

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

SCOTT                                   DEPT                                 USERS                             4194304

SCOTT                               PK_DEPT                               USERS                             4194304

SCOTT                          EMP                  USERS                             4194304

SCOTT                          PK_EMP               USERS                             4194304

SCOTT                          BONUS                USERS                             4194304

SCOTT                          SALGRADE             USERS                             4194304

SCOTT                          TEST                 USERS                             4194304

SCOTT                          T01                  USERS                             4194304

8 rows selected.

delete       删除数据    不会重置高水位   不会释放占用的数据块                        Truncate  删除数据   并且重置高水位  释放占用的数据块】

Execution Plan                                                                                                                                                   Execution Plan

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

Plan hash value: 1357081020                                                                                                                         Plan hash value: 1357081020

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

| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |                        | Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |

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

|   0 | SELECT STATEMENT  |      |     1 |    13 |    43   (3)| 00:00:01 |                              |   0 | SELECT STATEMENT  |      |     1 |    13 |     2   (0)| 00:00:01 |

|   1 |  TABLE ACCESS FULL| TEST |     1 |    13 |    43   (3)| 00:00:01 |                           |   1 |  TABLE ACCESS FULL| TEST |     1 |    13 |     2   (0)| 00:00:01 |

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

Execution Plan                                                                                                                                     Execution Plan

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

Plan hash value: 1357081020                                                                                                  Plan hash value: 1357081020

Statistics                                                                                                                                           Statistics

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

1 recursive calls                                                                                                                             1  recursive calls

0  db block gets                                                                                                                     0  db block gets

185  consistent gets                                                                                                               22  consistent gets

0  physical reads                                                                                                                    0  physical reads

0  redo size                                                                                                                             0  redo size

451  bytes sent via SQL*Net to client                                                                                 451  bytes sent via SQL*Net to client

384  bytes received via SQL*Net from client                                                                    384  bytes received via SQL*Net from client

2  SQL*Net roundtrips to/from client                                                                              2  SQL*Net roundtrips to/from client

0  sorts (memory)                                                                                                                 0  sorts (memory)

0  sorts (disk)                                                                                                                         0  sorts (disk)

2  rows processed                                                                                                                2  rows processed

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