Final answer:
Shutdown maintenance is a maintenance action performed at the beginning of an inactive period to prepare equipment for prolonged idleness.
Step-by-step explanation:
The maintenance action that prepares equipment for periods of prolonged idleness is called shutdown maintenance. It is usually performed only once at the beginning of the inactive period. Shutdown maintenance involves thorough inspection, cleaning, and preservation of equipment to ensure it remains in good condition until it is brought back into operation.