Configuration migration utility is part of Dynamics 365 SDK and located in SDK\Tools\ConfigurationMigration folder. Tool is used to import configuration/master data across CRM organizations. By default tool runs with 5 threads to import data and data import is comparatively slow.
You can increase number of threads to import data faster. Open DataMigrationUtility.exe.config file located in same folder SDK\Tools\ConfigurationMigration. Search for “numberofinputthreads” and change value from 5 to 20 or more based on requirement. Once updated tool will initialize 20 threads and data will be imported comparatively faster.