oracle 之数据字典屣履造门。（更新中）

今天是2013-06-20，哎，写这篇笔记的时候，我发现我是一个非常懒惰的人，这篇文章本该昨天就完成的，想起了钱鹤滩的《明日歌》，真是“世人若被明日累，春去秋来老将至”。
oracle数据字典包括四部分，分别是RDBMS(X$),数据字典表、动态性能视图（v$）和数据字典视图。
1)RDBMS(X$)内部 表：
该部分内容是oracle最低层的表数据，这些表维持着oracle的整个视图，就像我们人体的血液在我们人体流动维持生命一样。
因此这些表只能查看、研究不建议修改。oracle对修改内部表产生的后果不负责技术支持工作。 
在查看参数文件的时候我曾经提到x$ksppi和X$ksppcv这两个内部表。
研究内部表：
oracle@oracle:~> sqlplus "/as sysdba"

SQL*Plus: Release 11.1.0.6.0 - Production on 星期四 6月 20 20:38:47 2013

Copyright (c) 1982, 2007, Oracle.  All rights reserved.

连接到:
Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SYS@orcl#select open_mode from v$database;

OPEN_MODE
--------------------
READ WRITE

SYS@orcl#grant select on x$ksppi to xiaohai;
grant select on x$ksppi to xiaohai
                *
第 1 行出现错误:
ORA-02030: 只能从固定的表/视图查询

可以看出内部表不允许进行授权。
研究内部表方法如下：
SYS@orcl#set autotrace trace explain;
SYS@orcl#select * from v$parameter;

执行计划
----------------------------------------------------------
Plan hash value: 1128103955

------------------------------------------------------------------------------
| Id  | Operation         | Name     | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |          |     1 |  4414 |     1 (100)| 00:00:01 |
|*  1 |  HASH JOIN        |          |     1 |  4414 |     1 (100)| 00:00:01 |
|*  2 |   FIXED TABLE FULL| X$KSPPI  |     1 |   249 |     0   (0)| 00:00:01 |
|   3 |   FIXED TABLE FULL | X$KSPPCV |   100 |   406K|     0   (0)| 00:00:01 |
------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

1 - access("X"."INDX"="Y"."INDX")
       filter(TRANSLATE("KSPPINM",'_','#') NOT LIKE '#%' OR
              "KSPPSTDF"='FALSE' OR BITAND("KSPPSTVF",5)>0)
   2 - filter("X"."INST_ID"=USERENV('INSTANCE') AND
              TRANSLATE("KSPPINM",'_','#') NOT LIKE '##%')

SYS@orcl#

autotrace 语句研究：

该语句工具主要是研究统计sql语句的执行计划并生成报告，进而对dml语句进行检测和优化。
Generates a report on the execution path used by the SQL optimizer and the statement execution statistics. The report is useful to monitor and tune the performance of DML statements.

set  autotrace off;    不产生报告和执行计划，默认设置。
set autotrace on  explain;  生成执行计划并显示查询信息；
set autotrace on statistics；只生成语句的统计信息并显示查询信息。
set autotrace on ;   即生成语句报告有显示语句的执行统计信息和计划
set autotrace traceonly;  和on一样，区别就是不显示查询信息，查询的数据依然会fetch但是不会print，只显示统计信息和执行计划；
eg：
SYS@orcl#set autotrace on explain
SYS@orcl#select * from t2;

EMPNO ENAME
---------- --------------------
      7521 WARD

执行计划
----------------------------------------------------------
Plan hash value: 1513984157

--------------------------------------------------------------------------
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |     1 |    20 |     2   (0)| 00:00:01 |
|   1 |  TABLE ACCESS FULL| T2   |     1 |    20 |     2   (0)| 00:00:01 |
--------------------------------------------------------------------------

Note
-----
   - dynamic sampling used for this statement

SYS@orcl#set autotrace on statistices;
SP2-0735: 未知的 SET 选项开头 "statistice..."
SYS@orcl#set autotrace on statistics;
SYS@orcl#select * from t2;

EMPNO ENAME
---------- --------------------
      7521 WARD

统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          3  consistent gets
          0  physical reads
          0  redo size
        600  bytes sent via SQL*Net to client
        524  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed
SYS@orcl#select * from t2;

EMPNO ENAME
---------- --------------------
      7521 WARD

执行计划
----------------------------------------------------------
Plan hash value: 1513984157

--------------------------------------------------------------------------
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |     1 |    20 |     2   (0)| 00:00:01 |
|   1 |  TABLE ACCESS FULL| T2   |     1 |    20 |     2   (0)| 00:00:01 |
--------------------------------------------------------------------------

Note
-----
   - dynamic sampling used for this statement

统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          3  consistent gets
          0  physical reads
          0  redo size
        600  bytes sent via SQL*Net to client
        524  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed

SYS@orcl#

SYS@orcl#set autotrace traceonly;
SYS@orcl#select * from t;

执行计划
----------------------------------------------------------
Plan hash value: 1601196873

--------------------------------------------------------------------------
| Id  | Operation         | Name | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------
|   0 | SELECT STATEMENT  |      |     5 |   180 |     3   (0)| 00:00:01 |
|   1 |  TABLE ACCESS FULL| T    |     5 |   180 |     3   (0)| 00:00:01 |
--------------------------------------------------------------------------

统计信息
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          4  consistent gets
          0  physical reads
          0  redo size
       1184  bytes sent via SQL*Net to client
        524  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          5  rows processed

总结：该工具可以查看语句的统计信息可以变化命令使用非常灵活，

SYS@orcl#set autotrace
用法: SET AUTOT[RACE] {OFF | ON | TRACE[ONLY]} [EXP[LAIN]] [STAT[ISTICS]]
便于语句调优。在此记录加深一下印象。呵呵，原来这个工具还有多种花样。

X$kvit 内部表：英文名字叫：kernel layer performance layer information tables transitory instance parameters；

#select kvitval,kvittag,kvitdsc from x$kvit
  2  ;

KVITVAL KVITTAG              KVITDSC
---------- -------------------- --------------------------------------------------------------------------------
         1 ksbcpu               number of logical CPUs in the system used by Oracle
         0 ksbcpucore           number of physical CPU cores in the system used by Oracle
         0 ksbcpusocket         number of physical CPU sockets in the system used by Oracle
         1 ksbcpu_hwm           high water mark of number of CPUs used by Oracle
         0 ksbcpucore_hwm       high water mark of number of CPU cores on system
         0 ksbcpusocket_hwm     high water mark of number of CPU sockets on system
         1 ksbcpu_actual        number of available CPUs in the system
         1 ksbcpu_dr            CPU dynamic reconfiguration supported
     33456 kcbnbh               number of buffers
       25 kcbldq               large dirty queue if kcbclw reaches this
40 kcbfsp               Max percentage of LRU list foreground can scan for free

KVITVAL KVITTAG              KVITDSC
---------- -------------------- --------------------------------------------------------------------------------
         2 kcbcln               Initial percentage of LRU list to keep clean
       800 kcbnbf               number buffer objects
         0 kcbwst               Flag that indicates recovery or db suspension
         0 kcteln               Error Log Number for thread open
         0 kcvgcw               SGA: opcode for checkpoint cross-instance call
         0 kcvgcw               SGA:opcode for pq checkpoint cross-instance call

已选择17行。

SYS@orcl#
kcbldq和kcbfsp是关于dbwr进程进行脏数据写入磁盘的条件。

如下：

SYS@orcl#@getsp.sql
输入 par 的值:  db_large_dirty

NAME                           VALUE                PDESC
------------------------------ -------------------- --------------------------------------------------
_db_large_dirty_queue          25                   Number of buffers which force dirty queue to be wr
                                                    itten

SYS@orcl#

SYS@orcl#@getsp.sql
输入 par 的值:  db_block_max_scan

NAME                           VALUE                PDESC
------------------------------ -------------------- --------------------------------------------------
_db_block_max_scan_pct         40                   Percentage of buffers to inspect when looking for
                                                    free

SYS@orcl#

总结：从这些信息我们可以研究出了lru原理，知道了dbwr进行脏数据写入磁盘的条件。

为了学习，进行尝试修改如下：

SYS@orcl#alter system set "_db_block_max_scan_pct"=50 scope=spfile;

系统已更改。

SYS@orcl#startup force;
ORACLE 例程已经启动。

Total System Global Area  805875712 bytes
Fixed Size                  2148720 bytes
Variable Size             562038416 bytes
Database Buffers          234881024 bytes
Redo Buffers                6807552 bytes

数据库已经打开。
SYS@orcl#show parameter _db_block

NAME                                 TYPE                   VALUE
------------------------------------ ---------------------- ------------------------------
_db_block_max_scan_pct               integer                50
SYS@orcl#exit 
从 Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options 断开
oracle@oracle:~/test> sqlplus "/as sysdba"

SQL*Plus: Release 11.1.0.6.0 - Production on 星期四 6月 20 21:25:47 2013

Copyright (c) 1982, 2007, Oracle.  All rights reserved.

连 接到:
Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options

SYS@orcl#@getsp.sql
输入 par 的值:  db_block_max_scan
原值    2: where x.indx=y.indx and x.ksppinm like '%&par%'
新值    2: where x.indx=y.indx and x.ksppinm like '%db_block_max_scan%'

NAME                           VALUE                PDESC
------------------------------ -------------------- --------------------------------------------------
_db_block_max_scan_pct         50                   Percentage of buffers to inspect when looking for
                                                    free

SYS@orcl#

可以看到我们修改的实施在spfile中加入隐含参数，然后在数据启动初始化的时候会引用隐含参数的值。（不建议修改）

SYS@orcl#alter system reset "_db_block_max_scan_pct";     

系统已更改。

SYS@orcl#startup force;

2）数据字典表：
在创建数据库的时候安装sql.bsp文件进行创建，在数据库启动的时候进行先关字典表的创建。可以通过跟踪数据库启动的过程进行分析。
eg:
startup nomount;
alter session set events '10046 trace nam context level 12';
alter database mount;
alter database open;
如下是截取的跟踪文件信息：
509 CREATE TABLE USER$("USER#" NUMBER NOT NULL,"NAME" VARCHAR2(30) NOT NULL,"TYPE#" NUMBER NOT NULL,"PASSWORD" VARCHAR2(30),"DATATS#" NUMBER NOT NULL,"TEMPTS#" NUM        BER NOT NULL,"CTIME" DATE NOT NULL,"PTIME" DATE,"EXPTIME" DATE,"LTIME" DATE,"RESOURCE$" NUMBER NOT NULL,"AUDIT$" VARCHAR2(38),"DEFROLE" NUMBER NOT NULL,"DEFGRP        #" NUMBER,"DEFGRP_SEQ#" NUMBER,"ASTATUS" NUMBER NOT NULL,"LCOUNT" NUMBER NOT NULL,"DEFSCHCLASS" VARCHAR2(30),"EXT_USERNAME" VARCHAR2(4000),"SPARE1" NUMBER,"SPA        RE2" NUMBER,"SPARE3" NUMBER,"SPARE4" VARCHAR2(1000),"SPARE5" VARCHAR2(1000),"SPARE6" DATE) STORAGE (  OBJNO 22 TABNO 1) CLUSTER C_USER#(USER#)
    510 END OF STMT
    511 PARSE #1:c=0,e=456,p=0,cr=0,cu=0,mis=1,r=0,dep=1,og=4,tim=1371736252499680
    512 BINDS #1:
    513 EXEC #1:c=0,e=217,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=4,tim=1371736252499956
=====================
    480 PARSING IN CURSOR #1 len=637 dep=1 uid=0 oct=1 lid=0 tim=1371736252496043 hv=1077251290 ad='8fd93c08' sqlid='3cgdmzx03b36u'
    481 CREATE TABLE OBJ$("OBJ#" NUMBER NOT NULL,"DATAOBJ#" NUMBER,"OWNER#" NUMBER NOT NULL,"NAME" VARCHAR2(30) NOT NULL,"NAMESPACE" NUMBER NOT NULL,"SUBNAME" VARCHAR2        (30),"TYPE#" NUMBER NOT NULL,"CTIME" DATE NOT NULL,"MTIME" DATE NOT NULL,"STIME" DATE NOT NULL,"STATUS" NUMBER NOT NULL,"REMOTEOWNER" VARCHAR2(30),"LINKNAME" V        ARCHAR2(128),"FLAGS" NUMBER,"OID$" RAW(16),"SPARE1" NUMBER,"SPARE2" NUMBER,"SPARE3" NUMBER,"SPARE4" VARCHAR2(1000),"SPARE5" VARCHAR2(1000),"SPARE6" DATE) PCTFR        EE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 STORAGE (  INITIAL 16K NEXT 1024K MINEXTENTS 1 MAXEXTENTS 2147483645 PCTINCREASE 0 OBJNO 18 EXTENTS (FILE 1 BLOCK 121)        )
    482 END OF STMT
    483 PARSE #1:c=0,e=552,p=0,cr=0,cu=0,mis=1,r=0,dep=1,og=4,tim=1371736252496039
    484 BINDS #1:
    485 EXEC #1:c=0,e=205,p=0,cr=0,cu=0,mis=0,r=0,dep=1,og=4,tim=1371736252496308

当我们创建表的时候，其实是向先关数据字典写入数据，分别是obj$,con$,col$,tab$等等。可以跟踪sql语句进行分析。
当然了我们创建完表之后，可以通过包进行查看我们当时的ddl语句。
eg：
SYS@orcl#select table_name from user_tables where table_name='T';

TABLE_NAME
------------------------------------------------------------
T

SYS@orcl#select dbms_metadata.get_ddl('TABLE','T') FROM DUAL;

DBMS_METADATA.GET_DDL('TABLE','T')
--------------------------------------------------------------------------------

  CREATE TABLE "SYS"."T"
   (    "TABLESPACE_NAME" VARCHAR2(30) NOT NULL ENABLE,

SYS@orcl#SET LONG 20000
SYS@orcl#R
  1* select dbms_metadata.get_ddl('TABLE','T') FROM DUAL

DBMS_METADATA.GET_DDL('TABLE','T')
--------------------------------------------------------------------------------

CREATE TABLE "SYS"."T"
   (    "TABLESPACE_NAME" VARCHAR2(30) NOT NULL ENABLE,
        "USERNAME" VARCHAR2(30) NOT NULL ENABLE,
        "BYTES" NUMBER,
        "MAX_BYTES" NUMBER,
        "BLOCKS" NUMBER,
        "MAX_BLOCKS" NUMBER,
        "DROPPED" VARCHAR2(3)
   ) PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645

DBMS_METADATA.GET_DDL('TABLE','T')
--------------------------------------------------------------------------------
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT)
  TABLESPACE "USERS"

研究一下这个dbms_metadata包。

这个包的接受如下：
Overview
This pkg implements the mdAPI, a means to retrieve the aggregated
definitions of database objects as either XML docs. or their creation DDL,
or to submit the XML documents to execute the DDL.
-------------------------------------------------------------------
SECURITY
This package is owned by SYS with execute access granted to PUBLIC.
It runs with invokers rights, i.e., with the security profile of
the caller.  It calls DBMS_METADATA_INT to perform privileged
functions.
The object views defined in catmeta.sql implement the package's security
policy via the WHERE clause on the public views which include syntax to
control user access to metadata: if the current user is SYS or has
SELECT_CATALOG_ROLE, then all objects are visible; otherwise, only
objects in the schema of the current user are visible.
然后我们在看看这个function是get_ddl内容如下：
  FUNCTION get_ddl (
                object_type     IN  VARCHAR2,
                name            IN  VARCHAR2,
                schema          IN  VARCHAR2 DEFAULT NULL,
                version         IN  VARCHAR2 DEFAULT 'COMPATIBLE',
                model           IN  VARCHAR2 DEFAULT 'ORACLE',
                transform       IN  VARCHAR2 DEFAULT 'DDL')
        RETURN CLOB;
那么我刚刚传的参数是object_type为table，name为T。另外这个包还有很多功能，后续多多实践进行学习。
3）静态数据字典视图。

   包括dba_视图，all_视图，user_视图。上级包括下级。如dba_tables,all_tables,user_tables;
eg:
SYS@orcl#set autotrace traceonly explain;
SYS@orcl#select * from dba_tables;

Predicate Information (identified by operation id):
---------------------------------------------------

1 - access("KSPPI"."INDX"="KSPPCV"."INDX")
   4 - access("T"."BOBJ#"="CO"."OBJ#"(+))
   5 - access("CX"."OWNER#"="CU"."USER#"(+))
   7 - access("T"."DATAOBJ#"="CX"."OBJ#"(+))
   8 - access("O"."OWNER#"="U"."USER#")
  10 - access("T"."TS#"="TS"."TS#")
  12 - access("T"."FILE#"="S"."FILE#"(+) AND "T"."BLOCK#"="S"."BLOCK#"(+) AND
              "T"."TS#"="S"."TS#"(+))
  13 - access("O"."OBJ#"="T"."OBJ#")
14 - filter(BITAND("T"."PROPERTY",1)=0)
  15 - filter(BITAND("O"."FLAGS",128)=0)
  20 - filter("KSPPI"."KSPPINM"='_dml_monitoring_enabled')

SYS@orcl#select * from all_tables;

Predicate Information (identified by operation id):
---------------------------------------------------

1 - filter("O"."OWNER#"=USERENV('SCHEMAID') OR  EXISTS (SELECT 0 FROM
              "SYS"."OBJAUTH$" "OA",SYS."X$KZSRO" "X$KZSRO" WHERE "GRANTEE#"="KZ
SROROL" AND

"OA"."OBJ#"=:B1) OR  EXISTS (SELECT 0 FROM SYS."X$KZSPR" "X$KZSPR"
WHERE

"INST_ID"=USERENV('INSTANCE') AND ((-"KZSPRPRV")=(-45) OR (-"KZSPR
PRV")=(-47) OR

(-"KZSPRPRV")=(-48) OR (-"KZSPRPRV")=(-49) OR (-"KZSPRPRV")=(-50))
))

SYS@orcl#select * from user_tables;
Predicate Information (identified by operation id):
---------------------------------------------------

1 - access("KSPPI"."INDX"="KSPPCV"."INDX")
   4 - access("T"."BOBJ#"="CO"."OBJ#"(+))
   5 - access("CX"."OWNER#"="CU"."USER#"(+))
   7 - access("T"."DATAOBJ#"="CX"."OBJ#"(+))
   8 - access("T"."TS#"="TS"."TS#")
  10 - access("T"."FILE#"="S"."FILE#"(+) AND "T"."BLOCK#"="S"."BLOCK#"(+) AND
              "T"."TS#"="S"."TS#"(+))
  12 - filter("O"."OWNER#"=USERENV('SCHEMAID') AND BITAND("O"."FLAGS",128)=0)
  13 - filter(BITAND("T"."PROPERTY",1)=0)
  14 - access("O"."OBJ#"="T"."OBJ#")
  19 - filter("KSPPI"."KSPPINM"='_dml_monitoring_enabled')
显而易见了。呵呵。
4）动态视图
明天继续学习。。。。

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