1、Data Dictionary Contents and UsageObjectivesAfter completing this lesson, you should be able todo the following:Identify key data dictionary components Identify the contents and uses of the data dictionary Query the data dictionaryControl filesData files Redo log filesDatabaseData DictionaryDuring d

2、atabase creation, the Oracle server createsadditional object structures within the data files. Data dictionary tablesDynamic performance tablesData Dictionary TablesDynamic Performance TablesData DictionaryThe data dictionary is a set of read-only tables andviews that record, verify, and provide inf

3、ormationabout its associated database. Describes the database and its objectsIncludes two types of objects:Base tablesStore description of databaseCreated with CREATE DATABASEData Dictionary viewsSummarize base table information Created using catalog.sql scriptData Dictionary ContentsThe data dictio

4、nary provides information about:Logical and physical database structureDefinitions and space allocations of objectsIntegrity constraintsUsersRolesPrivilegesAuditingHow the Data Dictionary Is UsedThe data dictionary has three primary uses: The Oracle server uses it to find information about:UsersSche

5、ma objectsStorage structuresThe 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 CategoriesThe data dictionary consists of three main sets ofstatic views distinguished from each other

6、 by theirscope: DBA: What is in all the schemasALL: What the user can accessUSER: What is in the users schemaDBA_xxxUSER_xxxALL_xxxObjects owned by the current userObjects accessible by the current userAll of the objects in the databaseFull Notes Page for PracticesDynamic Performance TablesDynamic p

7、erformance views record current databaseactivity. Views are continually updated while the database is operationalInformation is accessed from:MemoryControl fileDBA uses dynamic views to monitor and tune the databaseDynamic views are owned by SYS userDML is not allowedQuerying the Data Dictionary and

8、 Dynamic Performance ViewsData dictionary and dynamic performance views canbe queried for information.A listing of views available can be retrieved by querying the DICTIONARY view.A listing of the columns and its contents can be accessed using DESCRIBE and SELECT.Column comments are available to ret

9、rieve more insight into what a column content means within a particular view.Data Dictionary ExamplesGeneral OverviewDICTIONARY, DICT_COLUMNSSchema objects DBA_TABLES, DBA_INDEXES, DBA_TAB_COLUMNS, DBA_CONSTRAINTSSpace allocationDBA_SEGMENTS, DBA_EXTENTSDatabase structureDBA_TABLESPACES, DBA_DATA_FILESSummaryIn this lesson, you should have learned how to:Use the data dictionary views to get information about the database and instanceObtain information about data dictionary views from DICTIONARY and DICT