For DSA configuration this parameter specifies the actual DSA session control name for the remote system.
For Ggate configuration this parameter is used to identify a host entry in the Ggate configuration file; this entry is a logical name only which can provide you with one of several different ways to access the same host. The equivalent parameter, which would be provided as a -SCID parameter if you were connecting through the Datanet Terminal Manager (or as the TSAP in the OSI world) will actually be found as one of several OSI/DIWS/DSA parameters in the configuration file on the Ggate server.