This is a potential security issue, you are being redirected to https://csrc.nist.gov.
System that supports a system-of-interest during its life cycle stages but does not necessarily contribute directly to its function during operation.
NIST SP 800-160 Vol. 1 from
A system that provides support to the life cycle activities associated with the system-of-interest. Enabling systems are not necessarily delivered with the system-of-interest and do not necessarily exist in the operational environment of the system- of-interest.
NIST SP 800-160 Vol. 2 from ISO/IEC/IEEE 15288:2015