我的Oracle 9i学习日志（9）--数据字典与动态性能视图及练习

一、数据字典

不仅是每个Oracle数据库的核心组件之一，也是所有数据库用户重要的信息资源；描述数据与对象的数据；包含只读的表和视图；存储在系统表空间；所有者为sys；由Oracle server维护；通过select语句访问。

执行数据定义语言 (definition language,DDL)语句或有些数据操纵语言  (data manipulation language ,DML) 语句时会更新数据字典。

包括两部分：

1、 基表(base tables)，在create database执行时（执行sql.bsq脚本）创建；用户不能直接访问因为它们是被加密的，无法用DML语句直接更新这些表，有一个例外，AUD$。基表举例：IND$，包含数据的索引信息。

2、数据字典视图，在执行 $ORACLE_HOME/rdbms/admin/catalog.sql，catproc.sql脚本时创建。

数据字典的内容：审计、用户被赋予的特权和角色、用户名字、完整性约束、资源的分配情况、逻辑和物理结构。

数据字典视图种类：

 

数据字典举例：

概览: DICTIONARY, DICT_COLUMNS

Schema objects: DBA_TABLES, DBA_INDEXES,DBA_TAB_COLUMNS, DBA_CONSTRAINTS

空间分配: DBA_SEGMENTS, DBA_EXTENTS

数据库结构: DBA_TABLESPACES,DBA_DATA_FILES

Data dictionary views are static views that answer questions such as:

• Was the object ever created?

• What is the object a part of?

• Who owns the object?

• What privileges do users have?

• What restrictions are on the object?

二、动态性能视图

虚表；记录当前数据库活动及活动状态；在数据库运行期间持续更新；可通过访问内存和控制文件获得的信息；用于数据库的监视和性能调优；所有者为sys；synonymous以v$开头；在V$FIXED_TABLE里列出所有这些表的名字。

DBA可以在这些视图上再创建视图。

The dynamic performance tables answer questions such as:

• Is the object online and available?

• Is the object open?

• What locks are being held?

• Is the session active?

举例：

•V$CONTROLFILE : Lists the names of the control files

•V$DATABASE : Contains database information from the control file.

•V$DATAFILE : Contains data file information from the control file

•V$INSTANCE : Displays the state of the current instance

•V$PARAMETER : Lists parameters and values currently in effect for the session

•V$SESSION : Lists session information for each current session

•V$SGA : Contains summary information on the system global area (SGA)

•V$SPPARAMETER : Lists the contents of the SPFILE

•V$TABLESPACE : Displays tablespace information from the control file

•V$THREAD : Contains thread information from the control file

•V$VERSION : Version numbers of core library components in the Oracle server

三、管理脚本命名规则

 

Practice 5: Using Data Dictionary and Dynamic Performance Views

1  Which of the following statements are true about the data dictionary?

a  The data dictionary describes the database and its objects.

b  The data dictionary includes two types of objects: base tables and data dictionary

views.

c  The data dictionary is a set of tables.

d  The data dictionary records and verifies information about its associated database.

答案： a ， b ， c ， d 。

2  Base tables are created using the  catalog.sql  script.

a  True

b  False

答案： b 。

解析：是在 create database 时创建， catalog.sql 是创建视图。

3  Which three of the following statements are true about how the data dictionary is used?

a  The Oracle server modifies it when a DML statement is executed.

b  It is used to find information about users, schema objects, and storage structures.

c  It is used by users and DBAs as a reference.

d  The data dictionary is a necessary ingredient for the database to function.

答案： b ， c ， d 。

4  Data dictionary views are static views.

a  True

b  False

答案： a 。

5  The information for a dynamic performance view is gathered from the control file.

a  True

b  False

答案： b 。

6  Which of the following questions might a dynamic performance view answer?

a  Is the object online and available?

b  What locks are being held?

c  Who owns the object?

d  What privileges do users have?

e  Is the session active?

答案： a ， b ， d ， e 。

7 Connect as SYSTEM/MANAGER and find a list of the data dictionary views.
8 Identify the database name, instance name, and size of the database blocks.
Hint: Query the V$DATABASE, V$THREAD, and V$PARAMETER dynamic
performance views.
9 List the name of the data files.
Hint: Query the V$DATAFILE dynamic performance view.
10 Identify the data file that makes up the SYSTEM tablespace.
Hint: Query the DBA_DATA_FILES data dictionary view to identify the SYSTEM
tablespace data file.
11 How much free space is available in the database and how much is already used?
Hints
- Query the DBA_FREE_SPACE data dictionary view to show how much free
space is available in the database.
- Query the DBA_SEGMENTS data dictionary view to display how much space is
already used.
12 List the name and creation date of the database users.
Hint: Query the DBA_USERS data dictionary view to list the name and the creation
of the database users.

本文转自 d185740815 51CTO博客，原文链接：http://blog.51cto.com/luotaoyang/284100，如需转载请自行联系原作者