It depends on where and how badly the line is broken. With a crack, the toilet may still flush and drain, but every flush sends sewage into the soil around the pipe. If drains are backing up, gurgling, or sewage appears in a tub or shower, stop using every fixture until the line is inspected.
Until then, use as little water as you can. Skip laundry, the dishwasher and long showers, since they push the most water down the line at once. Watch your lowest drains, usually a ground-floor tub, shower or floor drain, because a blocked line overflows at its lowest opening first.
Stop using everything if flushing pushes water up another drain or several drains back up at once. That points to a blockage or a collapsed sewer line, not just a crack. One honest limit: nobody can tell a crack from a collapse by the symptoms alone. A sewer camera inspection shows which one you have.
The city maintains the main under the street, and you maintain the line from your property to it. In Dallas, report a clogged or overflowing wastewater main by calling 311, or 214-670-3111 from outside city limits.
Treat any backup as a health hazard. The CDC notes that water containing sewage can cause diarrheal illness. Wear waterproof gloves and wash your hands, and your children’s hands, with soap and water after any contact.
Before the inspection, find your sewer cleanout and clear a path to it. The camera usually goes in there.