The optional WriteMask Attribute exposes the possibilities of a client to write the Attributes of the Node. The WriteMask Attribute does not take any user access rights into account, that is, although an Attribute is writable this may be restricted to a certain user/user group.
If the OPC UA Server does not have the ability to get the WriteMask information for a specific Attribute from the underlying system, it should state that it is writable. If a write operation is called on the Attribute, the Server should transfer this request and return the corresponding StatusCode if such a request is rejected. StatusCodes are defined in OPC 10000-4.
The AttributeWriteMask DataType is defined in 8.60.