Oracle Namespace 說明

Oracle Namespace 說明

一. 初識Namespace

            Oracle經過namespace來管理schema object的名字，關於Namespace 的定義，在官網文檔上沒有找到一個詳細的定義，在網上搜到一些相關信息：

SchemaObject Namespaces

            A namespace defines a group of object types, within whichall names must be uniquely identified—by schema and name. Objects in differentnamespaces can share the same name.
            The Oracle database usesnamespaces to resolve schema object references. When you refer to an object ina SQL statement, Oracle considers the context of the SQL statement and locatesthe object in the appropriate namespace. After locating the object, Oracleperforms the operation specified by the statement on the object. If the named object cannot be found in the appropriate namespace,then Oracle returns an error.
            Because tables and views are in the same namespace, a table and a view inthe same schema cannot have the same name. However, tables and indexesare in different namespaces. Therefore, a table and an index in the same schemacan have the same name.
            Eachschema in the database has its own namespaces for the objects it contains. Thismeans, for example, that two tables in different schemas are in differentnamespaces and can have the same name.

--以上解釋提到了幾點：

            1.每一個用戶都有本身對應的namespace來保存本身的對象

            2.表和視圖存放在同一個namespace，因此對於同一個用戶的表和視圖不能重名，可是表和索引是存放在不一樣的namespace，因此能夠重名。

            開始時，咱們提到Oracle 經過schema 和 name 來保證namespace中對象的惟一性。 在obj$ 字典裏owner# 對應用戶的ID。 經過以下SQL，咱們能夠查看他們之間的對應關係：

           

/* Formatted on 2011/7/21 15:41:26(QP5 v5.163.1008.3004) */

SELECT username,user_id

  FROM dba_users

WHERE user_id IN (SELECT DISTINCTowner# FROM obj$);

USERNAME                     USER_ID

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

SYS                                0

SYSTEM                             5

DBSNMP                            24

SYSMAN                            58

DAVE                              61

OUTLN                             11

MDSYS                             46

ORDSYS                            43

CTXSYS                            36

EXFSYS                            34

DMSYS                             35

WMSYS                             25

XDB                               38

ORDPLUGINS                        44

SI_INFORMTN_SCHEMA                45

OLAPSYS                           47

SCOTT                             54

ORACLE_OCM                        55

TSMSYS                            21

19 rows selected.

 

一個小示例驗證以上結論：

SYS@anqing2(rac2)> createtable anqing(id number);

Table created.

SYS@anqing2(rac2)>create index anqing on anqing(id);

Index created.

SYS@anqing2(rac2)>create view anqing as select * from anqing;

create view anqing asselect * from anqing

            *

ERROR at line 1:

ORA-00955: name isalready used by an existing object

 

如下類型的對象使用同一個namespace：

? Tables
? Views
? Sequences
? Private synonyms
? Stand-alone procedures
? Stand-alone stored functions
? Packages
? Materialized views
? User-defined types

 

以下類型的對象使用本身的namespace：

? Indexes
? Constraints
? Clusters
? Database triggers
? Private database links
? Dimensions

 

如下Non schema objects 使用本身的namespace：

? User roles
? Public synonyms
? Public database links
? Tablespaces
? Profiles
? Parameter files (PFILEs) and server parameter files (SPFILEs)

以上信息隨Oracle 版本不一樣，可能有出入。

 

二. 深刻研究Namespace

            先執行以下SQL，查看每一個namespace 對應名稱和它所包含的對象的個數：

/* Formatted on 2011/7/21 14:24:47(QP5 v5.163.1008.3004) */

  SELECTnamespace,object_type, COUNT (*)

    FROM (SELECTnamespace,

                 DECODE (o.type#,

                        0, 'NEXTOBJECT',

                        1, 'INDEX',

                        2, 'TABLE',

                         3, 'CLUSTER',

                        4, 'VIEW',

                        5, 'SYNONYM',

                        6, 'SEQUENCE',

                        7, 'PROCEDURE',

                        8, 'FUNCTION',

                        9, 'PACKAGE',

                        11, 'PACKAGEBODY',

                        12, 'TRIGGER',

                        13, 'TYPE',

                        14, 'TYPEBODY',

                        19, 'TABLEPARTITION',

                        20, 'INDEX PARTITION',

                        21, 'LOB',

                        22, 'LIBRARY',

                        23, 'DIRECTORY',

                        24, 'QUEUE',

                        28, 'JAVASOURCE',

                        29, 'JAVACLASS',

                         30, 'JAVARESOURCE',

                        32, 'INDEXTYPE',

                        33, 'OPERATOR',

                        34, 'TABLESUBPARTITION',

                        35, 'INDEXSUBPARTITION',

                        40, 'LOBPARTITION',

                        41, 'LOBSUBPARTITION',

                        42, 'MATERIALIZEDVIEW',

                        43, 'DIMENSION',

                        44, 'CONTEXT',

                        46, 'RULESET',

                         47, 'RESOURCEPLAN',

                        48, 'CONSUMERGROUP',

                        51, 'SUBSCRIPTION',

                        52, 'LOCATION',

                        55, 'XMLSCHEMA',

                        56, 'JAVADATA',

                         57, 'SECURITYPROFILE',

                        59, 'RULE',

                        62, 'EVALUATIONCONTEXT',

                        'UNDEFINED')

                   object_type

            FROM sys.obj$ o)

GROUP BYnamespace,object_type;

NAMESPACE OBJECT_TYPE          COUNT(*)

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

        4 INDEX                    2253

        2 TYPE BODY                 175

       51 UNDEFINED                   6

       21 CONTEXT                     5

         9 DIRECTORY                   6

        1 SYNONYM                 20122

        1 PACKAGE                   859

        1 VIEW                     3684

        1 PROCEDURE                  98

        3 TRIGGER                   164

       38 EVALUATION CONTEXT         12

        1 SEQUENCE                  138

        2 PACKAGE BODY              804

        1 INDEXTYPE                  10

        1 TYPE                     1953

       24 RESOURCE PLAN               3

        4 INDEX PARTITION           144

       25 XML SCHEMA                 25

        1 TABLE                    1619

        8 LOB                       541

       10 QUEUE                      23

       23 RULE SET                   15

        8 LOB PARTITION               1

       36 RULE                        4

        1 JAVA CLASS              16450

        1 NEXT OBJECT                 1

        1 FUNCTION                  268

        1 UNDEFINED                 660

        1 LIBRARY                   154

        32 JAVA DATA                 298

        5 CLUSTER                    10

       24 CONSUMER GROUP              5

        1 TABLE PARTITION           124

        1 OPERATOR                   57

       14 JAVA RESOURCE             775

35 rows selected.

 

            經過這個查詢結果，咱們能夠看到一些對象使用相同的namespace。 第一列的數字表明的就是namespace。 關於type#的定義，在Oracle的obj$基表建立的定義SQL 有明確的說明。

 

            先在$ORACLE_HOME/RDBMS/admin/bin 下查找sql.bsq腳本。sql.bsq主要記錄了ORACLE中的系統字典表的定義，好比過tab$,col$,obj$ 等，經過查詢這個文件能夠知道數據字典表的定義. 在sql.bsq裏面保存了相關的腳本信息，其中就有dcore.bsq 腳本，在該腳本里就能夠找到obj$ 表的定義SQL:

 

/* Formatted on 2011/7/21 14:42:51(QP5 v5.163.1008.3004) */

CREATE TABLE obj$                                           /*object table */

(

   obj#       NUMBER NOT NULL,                             /*object number */

   dataobj#   NUMBER,                           /*data layer object number */

   owner#     NUMBER NOT NULL,                         /*owner user number */

   name       VARCHAR2 ("M_IDEN") not null,                  /* object name */

namespace    number not null,         /* namespace of object (see KQD.H):*/

/* 1 = TABLE/PROCEDURE/TYPE, 2 =BODY, 3 = TRIGGER, 4 = INDEX, 5 = CLUSTER, */

                                                 /* 8 =LOB, 9 = DIRECTORY, */

  /* 10 = QUEUE, 11 = REPLICATIONOBJECT GROUP, 12 = REPLICATION PROPAGATOR, */

                                     /* 13 = JAVA SOURCE, 14 = JAVARESOURCE */

                                                /* 58= (Data Mining) MODEL */

  subname       varchar2("M_IDEN"),               /* subordinate tothe name */

  type#         number not null,                 /* object type(see KQD.H): */

  /* 1 =INDEX, 2 = TABLE, 3 = CLUSTER, 4 = VIEW, 5 = SYNONYM, 6 = SEQUENCE, */

             /* 7 =PROCEDURE, 8 = FUNCTION, 9 = PACKAGE, 10 = NON-EXISTENT, */

              /* 11= PACKAGE BODY, 12 = TRIGGER, 13 = TYPE, 14 = TYPE BODY, */

      /* 19= TABLE PARTITION, 20 = INDEX PARTITION, 21 = LOB, 22 = LIBRARY, */

                                             /* 23= DIRECTORY , 24 = QUEUE, */

    /* 25= IOT, 26 = REPLICATION OBJECT GROUP, 27 = REPLICATION PROPAGATOR, */

    /* 28= JAVA SOURCE, 29 = JAVA CLASS, 30 = JAVA RESOURCE, 31 = JAVA JAR, */

                 /* 32= INDEXTYPE, 33 = OPERATOR , 34 = TABLE SUBPARTITION, */

                                                 /* 35= INDEX SUBPARTITION */

                                                /* 82= (Data Mining) MODEL */

                                /* 92= OLAP CUBE DIMENSION,  93 = OLAP CUBE */

                   /* 94= OLAP MEASURE FOLDER, 95 = OLAP CUBE BUILD PROCESS */

  ctime         date not null,                       /*object creation time */

  mtime         date not null,                      /* DDLmodification time */

  stime         date not null,          /* specificationtimestamp (version) */

  status        number not null,            /* status ofobject (see KQD.H): */

                                     /* 1 =VALID/AUTHORIZED WITHOUT ERRORS, */

                         /* 2 =VALID/AUTHORIZED WITH AUTHORIZATION ERRORS, */

                            /* 3 =VALID/AUTHORIZED WITH COMPILATION ERRORS, */

                        /* 4 =VALID/UNAUTHORIZED, 5 = INVALID/UNAUTHORIZED */

  remoteowner   varchar2("M_IDEN"),     /* remote ownername (remote object) */

  linkname      varchar2("M_XDBI"),             /* link name(remote object) */

  flags         number,               /* 0x01 = extentmap checking required */

                                      /*0x02 = temporary object             */

                                     /*0x04 = system generated object      */

                                      /*0x08 = unbound (invoker's rights)   */

                                      /*0x10 = secondary object             */

                                      /*0x20 = in-memory temp table         */

                                      /*0x80 = dropped table (RecycleBin)   */

                                      /*0x100 = synonym VPD policies        */

                                      /*0x200 = synonym VPD groups          */

                                      /*0x400 = synonym VPD context         */

                                      /*0x4000 = nested table partition     */

  oid$          raw(16),        /* OID for typedtable, typed view, and type */

  spare1        number,                      /* sqlversion flag: see kpul.h */

  spare2        number,                             /*object version number */

  spare3        number,                                        /*base user# */

  spare4        varchar2(1000),

  spare5        varchar2(1000),

  spare6        date

)

  storage (initial 10k next 100k maxextents unlimited pctincrease 0)

 

            在obj$ 這個字典裏面，保存的是namespace的ID。 他們之間的對應關係在obj$裏有說明。

   namespace     number not null,         /* namespace ofobject (see KQD.H): */

1 = TABLE/PROCEDURE/TYPE,

2 = BODY,

3 = TRIGGER,

4 = INDEX,

5 = CLUSTER,

8 = LOB,

9 = DIRECTORY,

10 = QUEUE,

11 = REPLICATION OBJECT GROUP,

12 = REPLICATION PROPAGATOR,

13 = JAVA SOURCE,

14 = JAVA RESOURCE

58 = (Data Mining) MODEL

 

查看obj$中共有多少個不一樣的namespace：

SYS@anqing2(rac2)> select distinctnamespace from obj$ order by namespace;

  NAMESPACE

----------

        1

        2

        3

        4

        5

        8

        9

       10

       14

       21

       23

       24

       25

       32

       36

       38

       51

17 rows selected.

 

SYS@anqing2(rac2)> select distinct namespace from v$librarycache;

NAMESPACE

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

BODY

JAVA DATA

SQL AREA

OBJECT

PIPE

JAVA RESOURCE

TABLE/PROCEDURE

TRIGGER

INDEX

JAVA SOURCE

CLUSTER

11 rows selected.

 

注意：

            在這裏有一個問題，咱們經過distinct obj$ 和distinct v$librarycache 查看的值不對應，並且這個值與咱們obj$的註釋也不一致。 這個問題是關鍵，由於它能夠引出到底Namespace 是什麼。

 

看一下DSI405裏對library cache object所屬於的namespace的定義：

            1.Library cache objects are grouped in namespaces according to their type.

            2.Each object can only be of one type.

            3.All the objects of the same type are in the same namespace.

            4.A namespace may be used by more than one type.

            5. The most important namespace is called cursor (CRSR)and houses the shared SQL cursors.

 

            經過這段解釋，咱們能夠看出，咱們以前經過obj$ 看到的namespace 是不全的，由於像shared cursor這樣的library cache object根本就不在obj$裏。

 

能夠這樣來理解Namespace：

            Namespace是針對緩存在library cache裏的library cache object來講的。

            咱們以前在obj$裏也有namespace的定義，是由於library cache object有一部分的來源就是來自於數據庫裏已經存在的、固化的object的metadata。

 

在DSI405中關於library cache object所屬於的namespace的詳細說明：

            Currentlythere are 64 different object types but this number may grow at any time withthe introduction of new features. Examples of types are: cursor, table,synonym, sequence, index, LOB, Java source, outline, dimension, and so on. Not every type corresponds to a namespace. Actually, thereare only 32 namespaces which, of course, are also subject to increase at anytime.

            Youcan see the list of namespaces in the library cache dump.

            Whatis a certainty is that all the objects of the same type will always be storedin the same namespace. An object can only be of one type, hence the search foran object in the library cache is reduced to a search for this object in thecorresponding namespace.

            Somenamespaces contain objects of two or three different types.

 

These are some of themost commonly used namespaces:

            CRSR: Stores library objects of type cursor (sharedSQL statements)

           TABL/PRCD/TYPE: Stores tables, views, sequences,synonyms, procedure specifications, function specifications, packagespecifications, libraries, and type specifications

            BODY/TYBD: Stores procedure, function, package, and typebodies

            TRGR: Stores library objects of type trigger

            INDX: Stores library objects of type index

            CLST: Stores library objects of type cluster

 

            The exact number and name of namespaces in use depends on theserver features that are used by the application. For example, if theapplication uses Java, namespaces like JVSC (Java source) and JVRE (Javaresource) may be used, otherwise they will not be used.

            Note: These namespaces do not store tables, clusters, orindexes as such, only the metadata is stored.

 

            在obj$的註釋裏提到了KQD.H文件，這個是Oracle 的源代碼，咱們看不到它的內容，雖然這裏面有咱們全部namespace 和其對應的namespace id。 不過咱們能夠dump library cache，來查看該版本下全部namespace 的名稱。 版本不一樣，namespace 也可能不一樣。

 

--查看Oracle 版本

SYS@anqing2(rac2)> select * fromv$version where rownum=1;

BANNER

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

Oracle Database 10gEnterprise Edition Release 10.2.0.4.0 - Prod

 

SYS@anqing2(rac2)> oradebug setmypid

Statement processed.

--把librarycache dump 出來

SYS@anqing2(rac2)> alter session set events 'immediate trace name library_cachelevel 1';

Session altered.

--獲取tracefile 名稱和路徑

SYS@anqing2(rac2)> oradebug tracefile_name

/u01/app/oracle/admin/anqing/udump/anqing2_ora_18783.trc

 

[oracle@rac2 ~]$ cat/u01/app/oracle/admin/anqing/udump/anqing2_ora_18783.trc

/u01/app/oracle/admin/anqing/udump/anqing2_ora_18783.trc

Oracle Database 10g Enterprise EditionRelease 10.2.0.4.0 - Production

With the Partitioning, Real ApplicationClusters, OLAP, Data Mining

and Real Application Testing options

ORACLE_HOME =/u01/app/oracle/product/10.2.0/db_1

System name:    Linux

Node name:      rac2

Release:        2.6.18-194.el5

Version:        #1 SMP Tue Mar 16 21:52:43 EDT 2010

Machine:        i686

Instance name: anqing2

Redo thread mounted by this instance: 2

Oracle process number: 23

Unix process pid: 18783, image: oracle@rac2(TNS V1-V3)

*** 2011-07-21 19:23:32.578

*** ACTION NAME:() 2011-07-21 19:23:32.574

*** MODULE NAME:(sqlplus@rac2 (TNS V1-V3))2011-07-21 19:23:32.574

*** SERVICE NAME:(SYS$USERS) 2011-07-2119:23:32.574

*** SESSION ID:(128.4091) 2011-07-2119:23:32.574

LIBRARY CACHE STATISTICS:

namespace           gets hit ratio      pins hit ratio    reloads  invalids

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

CRSR        164017     0.978   4693745    0.999      373    123

TABL          62538     0.966  1408421     0.868   182957     0

BODY           1575     0.970     1937     0.967        8     0

TRGR            231     0.818      284     0.852        0     0

INDX             60     0.183      107     0.430        4     0

CLST            281     0.954      720     0.982        0     0

KGLT              0     0.000         0    0.000        0      0

PIPE              0     0.000         0    0.000        0      0

LOB               0     0.000         0    0.000        0      0

DIR               2     0.500         4    0.500        0      0

QUEU              3     0.000        13    0.462        1      0

OBJG              0     0.000         0    0.000        0     0

PROP              0     0.000         0    0.000        0      0

JVSC              0     0.000         0    0.000        0      0

JVRE              0     0.000         0    0.000        0      0

ROBJ              0     0.000        0     0.000        0     0

REIP              0     0.000         0    0.000        0      0

CPOB              0     0.000         0    0.000        0      0

EVNT          15773     1.000    15915     0.999        1     0

SUMM              0     0.000         0    0.000        0      0

DIMN              0     0.000         0    0.000        0      0

CTX               0     0.000         0    0.000        0      0

OUTL              0     0.000         0    0.000        0      0

RULS              1     0.000         3    0.667        0      0

RMGR          32159     1.000    39619     1.000        1     0

XDBS              7     0.286         7    0.000        0      0

PPLN              0     0.000         0    0.000        0      0

PCLS             0     0.000         0    0.000        0      0

SUBS              2     0.500         2    0.500        0      0

LOCS              0     0.000         0    0.000        0      0

RMOB              0     0.000         0    0.000        0      0

RSMD              0     0.000         0    0.000        0      0

JVSD              0     0.000         0    0.000        0      0

STFG              0     0.000         0    0.000        0      0

TRANS             0     0.000         0    0.000        0      0

RELC              0     0.000         0    0.000        0      0

RULE              0     0.000         0    0.000        0      0

STRM              0     0.000         0    0.000        0      0

REVC              1     0.000         0    0.000        0      0

STAP              0     0.000         0    0.000        0      0

RELS              0     0.000         0    0.000        0      0

RELD              0     0.000         0    0.000        0      0

IFSD              0     0.000         0    0.000        0     0

XDBC              1     0.000         1    0.000        0      0

USAG              0     0.000         0    0.000        0      0

MVOBTBL           1    0.000         1     0.000        0     0

JSQI              0     0.000        0     0.000        0     0

CDC               0     0.000         0    0.000        0      0

MVOBIND           1    0.000         1     0.000        0     0

STBO              0     0.000         0    0.000        0      0

HTSO              0     0.000         0    0.000        0      0

JSGA           9805     0.999  3152085     0.942   181763     0

JSET              7     0.000         7    0.000        0      0

TABL_T           20     0.400        20    0.000        8      0

CLST_T            0     0.000         0    0.000        0      0

INDX_T            2     0.000         2    0.000        0      0

NSCPD             0     0.000         0    0.000        0      0

JSLV              4     0.750         4    0.750        0      0

MODL              0     0.000         0    0.000        0      0

CUMULATIVE  286491     0.979   9312898    0.960   365116    123

第一列就是Oracle 10.2.0.4.0 版本下全部Namespace 的個數：共60個。 這個遠比咱們經過obj$ 查詢出來的多。

 

三. Oracle 11g 中dba_objects中的Namespace

在Oracle 11g裏面，dba_objects 視圖裏也添加了Namespace 的字段，從而幫助咱們查詢。如SQL:

/* Formatted on 2011/7/21 14:33:09(QP5 v5.163.1008.3004) */

  SELECTobject_type,namespace, COUNT (*)

    FROMdba_objects

GROUP BYobject_type,namespace

ORDER BYnamespace;

咱們能夠經過以下語句來查看哪些表裏都還有Namespace 字段：

/* Formatted on 2011/7/21 14:34:37(QP5 v5.163.1008.3004) */

SELECT *

  FROMdict_columns

WHERE column_name = 'NAMESPACE';

TABLE_NAME           COLUMN_NAME     COMMENTS

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

ALL_CONTEXT          NAMESPACE       Namespace of the active context

DBA_CONTEXT              NAMESPACE       Namespace of the context

DBA_GLOBAL_CONTEXT       NAMESPACE

DBA_POLICY_CONTEXTS     NAMESPACE       Namespace of the context

ALL_POLICY_CONTEXTS      NAMESPACE       Namespace of the context

USER_POLICY_CONTEXTS    NAMESPACE       Namespace of the context

DBA_REGISTRY             NAMESPACE

USER_REGISTRY            NAMESPACE

DBA_REGISTRY_HIERARCHY   NAMESPACE

DBA_REGISTRY_LOG         NAMESPACE

DBA_REGISTRY_HISTORY     NAMESPACE

DBA_HIST_LIBRARYCACHE    NAMESPACE

V$LIBRARYCACHE           NAMESPACE

V$DB_OBJECT_CACHE        NAMESPACE

GV$LIBRARYCACHE          NAMESPACE

GV$DB_OBJECT_CACHE       NAMESPACE

V$CONTEXT                NAMESPACE

GV$CONTEXT               NAMESPACE

V$GLOBALCONTEXT          NAMESPACE

GV$GLOBALCONTEXT         NAMESPACE

20 rows selected.

--這個是oracle10g的一個查詢結果，在Oracle 11g裏面，查詢結果有35個。

 

 

致謝：

            很是感謝dbsnake 在這個問題上對我指導。 解除了我在這個問題上的一些疑惑。