Taken from the Language Reference manual under Record Locking:
If a table is in the read-only state, then a record loaded from the table is locked. A locked record can not be saved or deleted. Read only is the preferred state, because it allows other users to load, modify, and then save the record.
The second sentence may seem to contradict the first, but it does not. When you start a process, and have a table in the read-only state, it is in read-only state for that process and that process only. If you start another process that allows users to access that same table that is locked in the first process, users are now able to load, modify and save records. The reason being is all tables will default to read-write access. If a table is set to read-only, it is set for a specific process and does not effect other processes.