What turns a regional patrol ship into a global one

When does an OPV, corvette, or frigate gain global rather than merely regional reach?

When it can self-deploy and sustain itself with enough crew capacity, food, fuel, spares, and repair support for operations beyond local bases.

An OPV becomes globally useful when it can self-deploy beyond its home region. Hull volume that appears inefficient beside a more heavily armed foreign counterpart may instead carry food, fuel, spare parts, workshops, and crew facilities. Weapon count alone cannot capture endurance and independence, which are operational capabilities in their own right.