Data Dictionary Contents and Usage参考.ppt

Data Dictionary Contents and Usage Objectives After completing this lesson, you should be able to do the following: Identify key data dictionary components Identify the contents and uses of the data dictionary Query the data dictionary Data Dictionary During database creation, the Oracle server creates additional object structures within the data files. Data dictionary tables Dynamic performance tables Data Dictionary The data dictionary is a set of read-only tables and views that record, verify, and provide information about its associated database. Describes the database and its objects Includes two types of objects: Base tables Store description of database Created with CREATE DATABASE Data Dictionary views Summarize base table information Created using catalog.sql script Data Dictionary Contents The data dictionary provides information about: Logical and physical database structure Definitions and space allocations of objects Integrity constraints Users Roles Privileges Auditing How the Data Dictionary Is Used The data dictionary has three primary uses: The Oracle server uses it to find information about: Users Schema objects 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 The data dictionary consists of three main sets of static views distinguished from each other by their scope: DBA: What is in all the schemas ALL: What the user can access USER: What is in the users schema Full Notes Page for Practices Dynamic Performance Tables Dynamic performance views record current database activity. Views are continually updated while the database is operational Information is accessed from: Memory Control file DBA uses dynamic views to monitor and tune the database Dynamic views are owned by SYS user DML is not allowed Querying the Data Dictionary and Dynamic Performance Views Data dictionary and dynam