You have to work to what is called the Minimum Equipment List, otherwise known as the MEL. If you write up a snag in the technical log, the continued operation of the aircraft would depend very much on the MEL. For example, it might say that you MUST have the standby horizon working, but, with 2 independent pressurisation controllers, one might be permitted to be unserviceable. But, each snag will have a specific timescale by when it must be fixed.