Integrity antonym12/24/2022 ![]() It resides in the SYSTEM tablespace, which is always online. The data dictionary is always available when the database is open. Some views are accessible to all Oracle users, and others are intended for database administrators only. Access the data dictionary views with SQL statements. The views of the data dictionary serve as a reference for all database users. Application developers who write programs that refer to the data dictionary should refer to the public synonyms rather than the underlying tables: the synonyms are less likely to change between software releases. Other Oracle products can reference existing views and create additional data dictionary tables or views of their own. The COMMENTS columns describing the tables and their columns are not cached unless they are accessed frequently. Parsing information is typically kept in the caches. All information is stored in memory using the least recently used (LRU) algorithm. Much of the data dictionary information is kept in the SGA in the dictionary cache, because Oracle constantly accesses the data dictionary during database operation to validate user access and to verify the state of schema objects. Cache the Data Dictionary for Fast Access Users should avoid naming their own schema objects with the same names as those used for public synonyms. The security administrator can also create additional public synonyms for schema objects that are used systemwide. Oracle creates public synonyms for many data dictionary views so users can access them conveniently. Public Synonyms for Data Dictionary Views This new information is then visible the next time the dictionary views are queried. Oracle also updates the data dictionary continuously to reflect changes in database structures, auditing, grants, and data.įor example, if user Kathy creates a table named parts, then new rows are added to the data dictionary that reflect the new table, columns, segment, extents, and the privileges that Kathy has on the table. ![]() No data in any data dictionary table should be altered or deleted by any user.ĭuring database operation, Oracle reads the data dictionary to ascertain that schema objects exist and that users have proper access to them. The security administrator must keep strict control of this central account. No Oracle user should ever alter ( UPDATE, DELETE, or INSERT) any rows or schema objects contained in the SYS schema, because such activity can compromise data integrity. ![]() The Oracle user SYS owns all base tables and user-accessible views of the data dictionary. Most users are given access to the views rather than the base tables. These views decode the base table data into useful information, such as user or table names, using joins and WHERE clauses to simplify the information. The views that summarize and display the information stored in the base tables of the data dictionary. Users rarely access them directly because they are normalized, and most of the data is stored in a cryptic format. Only Oracle should write to and read these tables. The underlying tables that store information about the associated database. The data dictionary consists of the following: Base Tables "The SYSTEM Tablespace" for more information about SYSTEM tablespaces Because the data dictionary is read-only, you can issue only queries ( SELECT statements) against it's tables and views. Use SQL statements to access the data dictionary. Not only is the data dictionary central to every Oracle database, it is an important tool for all users, from end users to application designers and database administrators. All the data dictionary tables and views for a given database are stored in that database's SYSTEM tablespace. The data dictionary is structured in tables and views, just like other database data.
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