RACF (Resource Access Control Facility) is the IBM security management product for its mainframe (large server) operating system, OS/390 (MVS) as well as for its VM operating system. RACF allows an enterprise to manage the biggest security threat in most enterprises: destruction of computing resources by its own employees. Since its first release in 1976, RACF has screened millions of mainframe users who are familiar with their logon identification as their "RACF userid.""
RACF gives access to a computer system only to users who have the authorization to use a requested resource (such as a file, a printer queue, space to run a program, and so forth). To do this, RACF identifies and authenticates a user, determines the resources to which the user is authorized, and logs and reports attempts to get access to protected resources by unauthorized users.
In OS/390, RACF is part of the Security Server.