Oracle Study之案例--DBMS_METADATA Package应用

oracle Study之案例--DBMS_METADATA Package应用

DBMS_METADATA：

      The DBMS_METADATA package provides a way for you to retrieve metadata from the database dictionary as XML or creation DDL and to submit the XML to re-create the object.

案例分析：

[oracle@RH6 ~]$ sqlplus '/as sysdba'

SQL*Plus: Release 11.2.0.1.0 Production on Mon Dec 8 14:36:29 2014

Copyright (c) 1982, 2009, Oracle.  All rights reserved.

Connected to:

Oracle Database 11g Enterprise Edition Release 11.2.0.1.0 - Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options

14:36:29 SYS@ test1 >desc dbms_metadata

FUNCTION GET_DDL RETURNS CLOB
 Argument Name                  Type                    In/Out Default?
 ------------------------------ ----------------------- ------ --------
 OBJECT_TYPE                    VARCHAR2                IN
 NAME                           VARCHAR2                IN
 SCHEMA                         VARCHAR2                IN     DEFAULT
 VERSION                        VARCHAR2                IN     DEFAULT
 MODEL                          VARCHAR2                IN     DEFAULT
 TRANSFORM                      VARCHAR2                IN     DEFAULT

Parameters

Table 87-8 GET_xxx Function Parameters

通过dbms_metadata.get_ddl Procedure分析在extent management（Local or  Dictionary）不同方式下创建table的对象属性

14:50:43 SYS@ test1 >select tablespace_name,contents,extent_management from dba_tablespaces;

TABLESPACE_NAME                CONTENTS  EXTENT_MAN
------------------------------ --------- ----------
SYSTEM                         PERMANENT DICTIONARY
SYSAUX                         PERMANENT LOCAL
TEMP1                          TEMPORARY LOCAL
USERS                          PERMANENT LOCAL
UNDOTBS2                       UNDO      LOCAL
TEMP2                          TEMPORARY LOCAL
INDX                           PERMANENT LOCAL
TMP3                           TEMPORARY LOCAL
TMP4                           TEMPORARY LOCAL
TEST1                          PERMANENT LOCAL
PERFS                          PERMANENT LOCAL
DICT1                          PERMANENT DICTIONARY
TBS_16                         PERMANENT LOCAL

从以上可以看到“USERS tablespace”extent management 为local方式，"DICT1 tablespace" extent management 为dictionary方式

1）获取emp表信息（存储在USERS表空间）

14:44:14 SCOTT@ test1 >set long 5000
14:44:35 SCOTT@ test1 >set linesize 140
14:44:47 SCOTT@ test1 >set pagesize 1000
14:44:54 SCOTT@ test1 >select dbms_metadata.get_ddl('TABLE','EMP') FROM DUAL
DBMS_METADATA.GET_DDL('TABLE','EMP')
--------------------------------------------------------------------------------
  CREATE TABLE "SCOTT"."EMP"
   (    "EMPNO" NUMBER(4,0),
        "ENAME" VARCHAR2(10),
        "JOB" VARCHAR2(9),
        "MGR" NUMBER(4,0),
        "HIREDATE" DATE,
        "SAL" NUMBER(7,2),
        "COMM" NUMBER(7,2),
        "DEPTNO" NUMBER(2,0),
         CONSTRaiNT "PK_EMP" PRIMARY KEY ("EMPNO")
  USING INDEX PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL KEEP FLASH_CACHE DEFAULT CE
LL_FLASH_CACHE DEFAULT)
  TABLESPACE "USERS"  ENABLE,
         CONSTRAINT "FK_DEPTNO" FOREIGN KEY ("DEPTNO")
          REFERENCES "SCOTT"."DEPT" ("DEPTNO") ENABLE
   ) SEGMENT CREATION IMMEDIATE
  PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL RECYCLE FLASH_CACHE DEFAULT CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "USERS"
  
14:44:55 SCOTT@ test1 >select dbms_metadata.get_ddl('INDEX','PK_EMP') FROM DUAL;
DBMS_METADATA.GET_DDL('INDEX','PK_EMP')
--------------------------------------------------------------------------------
  CREATE UNIQUE INDEX "SCOTT"."PK_EMP" ON "SCOTT"."EMP" ("EMPNO")
  PCTFREE 10 INITRANS 2 MAXTRANS 255 COMPUTE STATISTICS
  STORAGE(INITIAL 65536 NEXT 1048576 MINEXTENTS 1 MAXEXTENTS 2147483645
  PCTINCREASE 0 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL KEEP FLASH_CACHE DEFAULT
CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "USERS"

2）获取t1表信息（存储在DICT1表空间）

14:52:12 SCOTT@ test1 >select dbms_metadata.get_ddl('TABLE','T1') FROM DUAL;
DBMS_METADATA.GET_DDL('TABLE','T1')
--------------------------------------------------------------------------------
  CREATE TABLE "SCOTT"."T1"
   (    "ID" NUMBER(*,0),
        "NAME" VARCHAR2(10)
   ) SEGMENT CREATION IMMEDIATE
  PCTFREE 10 PCTUSED 40 INITRANS 1 MAXTRANS 255 NOCOMPRESS LOGGING
  STORAGE(INITIAL 40960 NEXT 40960 MINEXTENTS 1 MAXEXTENTS 505
  PCTINCREASE 50 FREELISTS 1 FREELIST GROUPS 1 BUFFER_POOL DEFAULT FLASH_CACHE DEF
AULT CELL_FLASH_CACHE DEFAULT)
  TABLESPACE "DICT1"

3）查看数据字典

14:58:23 SCOTT@ test1 >select table_name,TABLESPACE_NAME,PCT_FREE,PCT_USED,FREELISTS,INITIAL_EXTENT/1024,NEXT_EXTENT/1024 from user_tables;

TABLE_NAME TABLESPACE_NAME                  PCT_FREE   PCT_USED  FREELISTS INITIAL_EXTENT/1024 NEXT_EXTENT/1024
---------- ------------------------------ ---------- ---------- ---------- ------------------- ----------------
EMP        USERS                                  10                                        64             1024
T1         DICT1                                  10         40          1                  40               40

    从以上可以判断，对于存储在local管理的tablespace上的table，在创建时，Oracle默认会分配大小64k的extent，启用pct_free参数，而pct_used和freelists参数不再被使用。对于存储在dictionary管理的tablespace上的table，在创建时，Oracle默认会分配大小40k得extent，启用pct_free,pct_used,freelists参数。