Which one more safty mainframe systems or pc systems ?

Mainframe off course. There are many security procedures under MVS for example.

Mainframes is the most secure platform to secure the data till date. That is the reason why most of the top banks prefer MAINFRAMES to store their customer's data

Mainframes.Thats why we use mainframes to hold secured data like Banks,Financial Data

mainframe thats, why we use mainframe computers in processing huge volumes of data