One of a firm's most valuable resources is its data: Customer lists, accounting data, employee information, and so on. This critical data needs to be securely managed and controlled, and, simultaneously, made available to those users authorized to see it. The mainframe computer has extensive capabilities to simultaneously share, but still protect, the firm's data among multiple users.

In an IT environment, data security is defined as protection against unauthorized access, transfer, modification, or destruction, whether accidental or intentional. To protect data and to maintain the resources necessary to meet the security objectives, customers typically add a sophisticated security manager product to their mainframe operating system. The customer's security administrator often bears the overall responsibility for using the available technology to transform the company's security policy into a usable plan.

A secure computer system prevents users from accessing or changing any objects on the system, including user data, except through system-provided interfaces that enforce authority rules. The New Mainframe can provide a very secure system for processing large numbers of heterogeneous applications that access critical data.