The working principle of the Virtual Private Database technology is that users should have isolated and distinguished data access. Virtual Private Database (VPD) is a feature that is built on fine-grained access control and uses application contexts to define and add the predicates to the SQL queries. Similar to FGAC, Virtual Private Database lays down the security framework through the security policies in the Oracle Database and associates them directly to tables, views, or synonyms. The security policies act as a safety net on the objects, and by no means they can be bypassed.
Whenever a user issues an SQL query against a Virtual Private Database protected table, Oracle invokes the policy and evaluates the policy function. The policy function is a PL/SQL function that returns a predicate or a WHERE clause. The query is then rewritten using dynamic views to add the predicate clause. The modified query is executed against the...