An on-premise app just crashed. Apparently, the connection to the SQL server could not be made, but nothing changed in the configuration. Also logging into SQL Server return doesn't work. See for the error in the Mendix log below. After restarting the Windows Service SQL Server, everything works fine again. The ConnectionPoolingMaxActive is set to 100. The logfiles in the server do not clearify anything. My question is what are the best practices to find out the causes of this error and how to prevent this. ERROR - ConnectionBusRetrieve: JDBCDataStore::execRetrieveQuery failed with SQLState: 08S01, error code: 0, message: Connection reset by peer: socket write error ERROR - ConnectionBusRetrieve: com.microsoft.sqlserver.jdbc.SQLServerException: Connection reset by peer: socket write error INFO - ConnectionBus_Retrieve: Trying to clean up and reset connection pooling mechanism... ERROR - ConnectionBus: Error on closing JDBC connection. Already closed.