3.9 Ensure database integrity
                 -------------------------

- Managing constraints.

   Q: What is a query that gives a DBA the primary/foreign key
      relationships of tables within the database.

   A:
     >>> Begin of script
     rem   ???????Check this script ?????????
     column For_owner format a10
     column For_table format a10
     column Pri_owner format a10
     column Pri_table format a10
     column For_col format a15
     column Pri_col format a15
     rem
     select A.Owner For_owner, A.Table_name For_table,
            C.Column_name For_col, B.Owner Pri_owner,
            B.Table_name Pri_table, D.column_name Pri_col
     from DBA_CONSTRAINTS A, DBA_CONSTRAINTS B,
          DBA_CONS_COLUMNS C, DBA_CONS_COLUMNS D
     where A.R_constraint_name = B.constraint_name
     and  A.Constraint_type = 'R'
     and  B.Constraint_type = 'P'
     and  A.R_owner         = B.owner
     and  A.Constraint_name = C.Constraint_name
     and  B.Constraint_name = D.Constraint_name
     and  A.Owner           = C.Owner
     and  A.Table_name      = C.Table_name
     and  B.Owner           = D.Owner
     and  B.Table_name      = D.Table_name;
     >>> End of script

- Data dictionary view for constraints.

             3.9 Overview of database privileges
                 --------------------------------

- System privileges and object privileges.

  !!! Important note:

         If user A has CREATE ANY object privilege (i.e.
         CREATE ANY TABLE) and creates an object in user B schema
         (for example, CREATE TABLE B.T (C char(1);) then the
         owner of object being created is user B rather then
         A (in out example user the owner of table T is B
         despite of this table  was created by user A). This
         rules are extended on all types of objects

   !!! End of important note


- Grant and revoke privileges.

- Managing roles.

  There is a very CONFUSING thing in Oracle 7.0, 7.1, ...

  Three pre-defined roles exist:
    CONNECT
    RESOURCE
    DBA.

  These roles were designed for compatibility with Oracle
  v6. Several privileges are assigned to them.  But there is one
  EXCEPTION:

   Statements:

       grant RESOURCE to <Object>;

                 and

       grant DBA to <Object>;

    implicitly execute the statement:

       grant UNLIMITED TABLESPACE to <Object>;

    Similarly, the statements:

       revoke RESOURCE to <Object>;

          and

       revoke DBA to <Object>;

        implicitly execute

        revoke UNLIMITED TABLESPACE to <Object>;

       If a user has UNLIMITED TABLESPACE privilege he can write
       to any tablespace IGNORING ANY QUOTAS.

       Granting CONNECT role does not causes any extra
       privileges!