A z/VSE user configured a session between VTAM and PU2.0 through OSA-Express and XCA major nodes. When the PU2.0 sent a connection request , with the PU status in VTAM not CONCT, VTAM issued diagnostic messages IST690I, IST081I, and IST314I, as follows:
IST690I CONNECTION REQUEST DENIED - INVALID STATION ID = stationid
IST081I LINE NAME = linename, LINE GROUP = groupname, MAJNOD = nodename
Diagnosing the problem
The diagnostic messages are the result of a long-standing restriction on using switched dial-in XCA connections on VSE VTAM. This restriction is now removed by New Function APAR DY30201.
There are many PU2.0 devices that do not send a null XID as the first XID to negotiate a connection request. Instead, they send an XID0. Prior to new function APAR DY30201, The VSE VTAM support for XCA did not accept an XID0 on a dial-in request. VSE VTAM required a null XID on a dial-in request. XID format0 could only be accepted as an XID response.
In short, on a switched dial-in XCA connection, VSE VTAM required that a null XID be sent in from the PU to set up the connection. If an XID0 or XID1 was sent in from the device while in LSN_SW_IN_POLL_PENDING state, the XID was discarded by VSE VTAM as an unexpected XID.
Resolving the problem