From OpenSCADAWiki
The result of the request is marked in the response by setting the rez attribute to the value: 0-successful, 1-warning, 2-error. In the event of an error the message is written to the "text" of the tag and the attribute "mcat" (the message category) — <{req} path="{path}" user="{user}" rez="2" mcat="/sub_DAQ/mod_BlockCalc">Impossible to remove the node</{req}>. In the event of a warning the message is written to the attribute "mtxt" and the attribute "mcat" (the message category) with storing the main tag's data — <{req} path="{path}" user="{user}" rez="1" mcat="/sub_DAQ/mod_BlockCalc" mtxt="Restart after the operation!">{main data}</{req}>.