There are many reasons why a fire sprinkler system fails to control a fire.
If fire water supply is not available at the minimum pressure and volume for which the system is designed, one has to hope for the best and wait for the fire department to arrive. During a field investigation of a building up for an expansion, I normally check the existing life safety systems to verify what I have to work with. Verifying fire alarm status and fire water flow data is part of that investigation.