The <modelname>_io.json file, for example transport_io.json , holds the GAMS/MIRO data contract and is located in the <modelname>/conf_<modelname> directory. It contains the metadata of all input and output symbols defined between the $onExternalInput / $offExternalInput and $onExternalOutput / $offExternalOutput tags in the corresponding GAMS model. The <modelname>_io.json file is created each time a MIRO app ist started via GAMS Studio and should not be changed. If you use the command line, please follow these steps.