The previous answer is absolutely correct, it is a Proprietary Data Base, developed by ABB. However, additionally the data can be accessed via SQL commands, either directly via an SQL Client or by utilizing and ODBC Client. Also, there are other methods to access the data. The latest version of 800xA History contains an OPC-UA Server for DA and HDA data access and and OPC Server for A/E data access. All this information is available in the 800xA History manuals included with each system.