The Structured Field for MSDM Access is not documented in the Security guide and there is no SXCTL field defined causing the problem that MSDM access cannot be defined using SEC=NMSAFF.
This field determines the level of function provided by MAI Stored Definition Maintenance (/MSDM). Values greater than 0 are only allowed for Privilege Class A users. Valid values are:
3 - Enables the user to update and delete all session models. 2 - Enables the user to update but not delete all session models. 1 - Enables the user to list and browse all session models. Update access is allowed to the session model with the same name as the user ID. 0 - Access is restricted to updating the session model with the same name as the user ID.