Resource Access Control Facility

RACF, [pronounced Rack-Eff] short for Resource Access Control Facility, is an IBM software product. It is a security system that provides access control and auditing functionality for the z/OS and z/VM operating systems. RACF was introduced in 1976.
Its main features are:
RACF establishes security policies rather than just permission records. It can set permissions for file patterns — that is, set the permissions even for files that do not yet exist. Those permissions are then used for the file (or other object) created at a later time .
RACF has continuously evolved to support such modern security features as digital certificates/public key infrastructure services, LDAP interfaces, and case sensitive IDs/passwords. The latter is a reluctant concession to promote interoperability with other systems, such as Unix and Linux. The underlying zSeries (now IBM Z) hardware works closely with RACF. For example, digital certificates are protected within tamper-proof cryptographic processors. Major mainframe subsystems, especially DB2 Version 8, use RACF to provide multi-level security (MLS).
Its primary competitors have been ACF2 and TopSecret, both now produced by CA Technologies.