in MS SQL Server you are able to make an entry of SESSION_CONTEXT read-only by passing the @read_only param to the sp_set_session_context function:
"[ @read_only= ] { 0 | 1 } A flag of type bit. If 1, then the value for the specified key cannot be changed again on this logical connection. If 0 (default), then the value can be changed."
The equalient SET command could look something like:
SET READONLY my_app.some_var = 'foo';
SET READONLY SESSION my_app.some_var = 'foo';
SET READONLY LOCAL my_app.some_var = 'foo';
Of course read-only would default to false for backwards compatibility.
When setting READONLY for on SESSION config then that config is not allowed to be changed anymore until the connection gets closed - even when running RESET ALL or DISCARD ALL.
