The service type defines the Adaptive Server service as either MASTER or QUERY.
MASTER defines the service that Adaptive Server uses to listen to login requests from clients. This type defines a server machine.
A MASTER entry is required only if you plan to use your computer as a server; it is not required for a computer that is running clients only.
QUERY represents the service that a client application uses to log in to Adaptive Server. This type defines a client machine.
A QUERY entry is required if you plan to use your computer to access a server. In general, since even dedicated servers need access to other servers, a QUERY entry is always required.