IBM System Management Facilities
IBM SMF is a feature of IBM's z/OS for mainframe computers. SMF provides full "instrumentation" of all baseline activities running on that IBM mainframe operating system, including I/O, network activity, software usage, error conditions, processor utilization, etc. SMF forms the basis for nearly all monitoring and automation utilities. Each SMF record has a numbered type (e.g. "SMF 120" or "SMF 89"), and operators have great control over how much or how little SMF data to collect. The special Service Assist Processors (SAP) in IBM mainframes play a key role in helping to create SMF records without unduly burdening the main processors.
SMF is technically a priced (extra cost) feature of z/OS, primarily because BMC sells a competing alternative called CMF. SMF is the more popular of the two.