IST690I on switched dial-in connection attempt from PU2.0 over XCA
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
New function APAR DY30201 removes this restriction. For all VSE VTAM customers using XCA connections, DY30201 allows a switched XCA PU to iniitate a connection request with an XID0 or an XID1. Apply DY30201 (PTF UD53626) to exploit this new function.