Data dictionary in oracle

The tables in oracle's data dictionary static data dictionary cannot be accessed directly. However, you can access the view in the data dictionary. The views in the static data dictionary are divided into three types: USER _, ALL _, and DBA _. Three types of View data overlap, except for different access ranges, all of which are consistent. USER _ stores information about objects owned by the current USER (that is, all objects in the current USER mode ). The ALL _ view stores information about ALL objects that the current user can access. You must have the permission to access this object. DBA _ view stores the information of all objects in the database. Generally, administrator permissions are required.
1. USER_USERS view current user information www.2cto.com 2. USER_TABLES view information of all tables owned by the current user 3. USER_OBJECTS view information of all objects owned by the current user 4. table-level permissions of the current user in the USER_TAB_PRIVS view 5. USER_SYS_PRIVS view system permissions of the current user 6. USER_INDEXES7.USER_IND_COLUMNS information of the field indexed 8. USER_SEGMENTS: Check the segment information. You can also calculate the index size. USER_SEQUENCES 10. USER_VIEWS11.USER_SYNONYMS view the synonym name 12. USER_CONSTRAINTS13.USER_CONS_COLUMNS. USER_SOURCE allows you to view the source code of functions and processes.
Dynamic Data Dictionary: some potential tables and views maintained by the system administrator, which are constantly updated during database operation. Provides information about the memory and disk running status, so you can only perform read-only access to it, but cannot modify it. These dynamic performance views start with V $. The following are the main views: 1.V$ ACCESS describes the database objects locked in the database and the session objects accessing these objects (session objects) 2.V$ SESSION describes the details of the current SESSION. www.2cto.com 3.V$ ACTIVE_INSTANCE describes the information of the active instances in the current database.
4. V $ CONTEXT describes the attributes of the current session, such as namespaces and attribute values. Multiple data dictionaries: USER _, ALL _, DBA _, V $, GV $, V _ $, GV _ $, X $ GV $, and G indicates Global. Except for some special cases, each V $ view has a corresponding GV $ view. The GV $ view appears in the parallel server (OPS) environment. In the parallel server environment, the GV $ view returns all instance information, while the V $ view adds the instance ID judgment result based on the GV $ view, that is, each V $ view is generated by the statement where inst_id = USERENV ('instance') in the GV $ view. V $ and GV $ are actually synonyms of GV _ $ and V _ $ views. In fact, the V $ view is directly created based on the X $ table. X $ table is the basis for running oracle databases. It is dynamically created by oracle Applications When the database is started. Author mark_qi