SNA exchange identifiers

To establish a connection, your system and the remote device both send an SNA exchange identifier (XID).

The exchange identifier is defined in the controller description for your system. SNA hosts that use parallel connections require the XIDs. Your system conducts an initial poll with NULL XIDs during the connection process to determine whether the remote device is active. If the device responds to the poll, your system and the remote device exchange XIDs and establish the connection.

The controller description for an SNA host names the XID value as the local exchange identifier. The APPC controller description names the XID value as the exchange identifier. Other controller types, such as CTRL, FNC, and RWS, also use the exchange identifier.