.dbc represent Database Connection file.
.dbc is a abinitio defined file which is used to establish the connection between database server and Abinitio server.
.cfg represent UNIX defined, UNIX level configuration file which is an auto parameter driven shell script that is submitted to the Korn shell.
multi-environment variables are declared in .cfg file.
.cfg files are older version of database configuration files used with 2.1 database components.