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.
