Using the global parameter sql_mode you can specify whether MaxScale should by default expect regular MariaDB SQL or PL/SQL.

That is inconvenient if some of the applications expect the former and some the latter and requires that either group set the right mode using set sql_mode=[oracle|default] at runtime.

If sql_mode was made into a service parameter, you could have one service expecting MariaDB SQL and another service expecting PL/SQL, and have the client connect to the service that has the right default. That way applications would not have to set the mode explicitly.