VPD uses a type of query REWRITE to restrict users to CERTAIN ROWS of TABLES and views. a security policy is attached to the table or tables to which we want to control access,and stored procedures are written to modify any relevant SQL statements made against the tables in the question. For example, when a user issues an UPDATE statement against the table with such a security policy, Oracle will dynamically append a predicate(a WHERE clause)to the user's statement to modify it and limit the user's access to that table. This will prevent users belonging to say SALES department from accessing and modifying FINANCE department records.

UPDATE emp set salary=salary*10 will be modified as UPDATE emp set salary=salary*10 where dept='SALES';.

VPD uses a type of query rewrite to restrict users to certain rows of tables and views. a security policy is attached to the table or tables to which we want to control access,and stored procedures are written to modify any relevant SQL statements made against the tables in the question. For example, when a user issues an UPDATE statement against the table with such a security policy, Oracle will dynamically append a predicate(a WHERE clause)to the user's statement to modify it and limit the user's access to that table. This will prevent users belonging to say SALES department from accessing and modifying FINANCE department records.

UPDATE emp set salary=salary*10 will be modified as UPDATE emp set salary=salary*10 where dept='SALES';.