Types:
1. Data dictionary tables ---> reflect the database's information; describes the database and its objects
2. Dynamic performance tables ---> reflect the instance's information
[@more@]Data Dictionary Tables Contents:
--- Logical and physical database structure
--- Definitions and space allocations of objects
--- Integrity constraints
--- Users
--- Roles
--- Privileges
--- Auditing
All of them shows that it describes the Oracle Database not instance
Types of Data
Dictionary Tables:
1. Base tables
--- Store description of database
--- Created with CREATE DATABASE
2. Data Dictionary views
--- Summarize base table information
--- Created using catalog.sql script
Data
Dictionary Tables Usage:
--- The Oracle server uses it to find informationabout: (1)Users,(2)Schema objects,(3)Storage structures.
--- The Oracle server modifies it when a DDL statement is executed.
--- Users and DBAs can use it as a read-only reference for information about the database.
Data
Dictionary View Categories:
--- DBA: What is in all the schemas --->DBA_xxx
--- ALL: What the user can access --->ALL_xxx
--- USER: What is in the user's schema --->USER_xxx
Dynamic Performance Tables: ---> V_$xxx | V$xxx | Vxxx
--- Dynamic performance views record current database activity(that is the instance).
--- Views are continually updated while the database is operational.
--- Information is accessed from: Memory,Control file
--- Dynamic views are owned by SYS user
--- DML is not allowed
--- DBA uses dynamic views to monitor and tune the database
Querying the Data Dictionary and Dynamic Performance Views:
1. To get an overview of the data dictionary and dynamic performance views, the DICTIONARY view or its synonym DICT can be queried.
eg:
SELECT * FROM dictionary;
SELECT * FROM dictionary WHERE table_name like 'DBA_%';
--- The V$FIXED_TABLE view can also be queried to get a listing of the views:
eg:
SELECT * FROM V$FIXED_TABLE;
2. To get a list of columns within a view, use the DESCRIBE keyword:
eg:
DESCRIBE V$INSTANCE;
3. To get an overview of the columns in the data dictionary and dynamic performance views,the DICT_COLUMNS view can be queried.
eg:
SELECT * FROM DICT_COLUMNS ORDER BY TABLE_NAME;
4. To view the contents of the view use the SELECT command.
eg:
SELECT * from V$INSTANCE;
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