computer security

a) In Databases you implement something called Two-phase Update. What is that and why do you do it? b) What is considered to be Sensitive data can vary depending on many different factors. Describe some of the reasons data might be seen as Sensitive data and typical examples of Sensitive data. c) A typical security related attack on databases is the Inference attack. What is the goal with such an attack and how is performed? (4+4+4 p)