Is Serializable Isolation the Best Option?

So the pattern is you query for some business requirement. There has to be at least two doctors on call, right? The application then decides what to do with those query results. And this again is that select for update that outlaw was talking about earlier. So as soon as you read the record for Dr. 1, it's locking that record and it's not released until you've either updated or just released the transaction. That could throw some sort of error or something or roll it back to whatever the state is.