The first knowledge dictionary "Weber products must be a boutique"

2. Data dictionary Structure

   There are two components:

   1. base table: System tables in $ end, Oracle automatically created tables when database is created

   2. Views that the user can access

3. types of data dictionaries

   DICTIONARY: Abbreviated DICT, all data dictionaries can be viewed through dict

   2.  DBA: SYS user owned by default, ordinary users can not access, only the SYS authorization, to access, stored all the relevant information
      to view the data dictionary at the beginning of the DBA:

       select  table_name from  dict where  table_name like  " dba%  Span style= "color: #800000;" > ' ; 

      table_name
      ------------------------------
      dba_roles
      dba_profiles
      Dba_catalog
      Dba_clusters
      Dba_clu_columns
      dba_col_comments
      Dba_col_privs
      dba_encrypted_columns

      ....

      525 rows selected.

      Sql> Select Owner,table_name from dba_tables where owner= ' SCOTT ';

      OWNER table_name
      ------------------------------------------------------------
      Scott DEPT
      Scott EMP
      Scott BONUS
      Scott Salgrade

   4. all begins with: data that the current user can access, can be divided into two parts of the data: part of the current user's own data, part of the other user's data, but the current user has access to the permissions, ordinary users can access
      such as: all_tables: View the table that the current user can access

       sql> select  owner,table_name from  all_tables ORDER by 1 ; 

      OWNER table_name
      ------------------------------------------------------------
      Wmsys aq$_wm$event_queue_ table_s
      Wmsys aq$_wm$event_queue_table_t
      Wmsys aq$_wm$event_queue_table_h
      Wmsys sys_iot_over_10282

      ..... ............

      1576 rows selected.

       conn Hr/hrgrant  select   on employees to Scott;conn Scott /tigersql  > select  owner,table_name from  all_tables ORDER by 1 ;--employees table will be displayed because Scott has access permissions 

   6. User starts with: Current users ' own data

      For example User_tables: The current user's own table

      Sql> Conn scott/tigerconnected.sqlSelect from user_tables; USER                   table_name------------------------------------------------------------SCOTT                   Deptscott                   Empscott                   Bonusscott                   Salgrade

   7. v$ starting with: Dynamic performance view
      V$fixed_table: You can view the dynamic performance view at the beginning of all v$ in the database

       is " SYS " SQL> desc v$fixed_table Name                                   Null?      ----------------------------------------------------------------- -------- -------------------------------------- ------ NAME                                        VARCHAR2 (object_id) number                                    TYPE                                        VARCHAR2 (5  ) Table_num                                     number

      Content of the dynamic performance view:

      1. Control the contents of the file

      2. In-memory data

      3. Dynamic performance view reflects the performance of the database

      4. The data in the dynamic performance view changes as the memory and the state of the database change as the data in memory changes in time

      Sql>The shutdown abortoracle routine has been closed. SQL>The startup Nomountoracle routine has been started. Total System Global Area608174080bytesfixed Size1275128bytesvariable Size184552200Bytesdatabase Buffers419430400Bytesredo Buffers2916352Bytessql>SelectStatus fromv$instance; STATUS------------------------------------Startedsql>ALTER DATABASE Mount; SQL>SelectStatus fromv$instance; STATUS------------Mountedsql>ALTER DATABASE open; SQL>SelectStatus fromv$instance; STATUS------------OPEN

      When do I access dynamic performance view?

      1. When a performance problem occurs in the database

      2. Accessing the contents of the control file

The first knowledge dictionary "Weber products must be a boutique"