Final answer:
The phase not part of the information system lifecycle is diagnosis. The lifecycle typically includes phases such as construction, transition, elaboration, and retirement.
Step-by-step explanation:
The phase that is not part of the life cycle that an information system goes through is diagnosis. The typical phases of an information system lifecycle include Construction, where the system is built; Transition, where it is deployed or moved to a different stage;
Elaboration, where the system is further developed or enhanced; and Retirement, where the system is phased out. Diagnosis is more generally associated with troubleshooting or problem-solving within the system's operation, rather than being a distinct phase of its lifecycle.