EE virtual node route selected after UNRCHTIM is detected

When an Enterprise Extender VRN is selected by VTAM® Topology and Routing Services, a DIAL request is made using the dynamic PU. The session remains in ADIALIP status until the DIAL request completes or until there is a timeout on the connection.

If there is a problem with the physical connection underlying the path through the VRN, the dynamic PU eventually receives an INOP because of the timeout. The following messages are received:

     IST259I   INOP RECEIVED FOR CNV00074 CODE = 01 
     IST1411I   INOP GENERATED FOR linename
     IST1430I   REASON FOR INOP IS XID OR LDLC COMMAND TIMEOUT 
             .
             . 
     IST1903I   FAILURE OVER vrnname TO CP partner_cpname 
     IST2050I   THIS PATH WILL NOT BE SELECTED FOR UNRCHTIM = seconds            
                          SECONDS 
     IST314I   END

Next, the session fails with sense 08010000. This is normal processing.

When a DISPLAY NET,TOPO,LIST=UNRCHTIM command is entered, the path is now shown as unreachable:

      IST2057I   UNREACHABLE PARTNER INFORMATION: 
      IST924I   - - - - - - - - - - - - - - - - - - - - - - - - - - 
      IST2150I   VIRTUAL NODE vrnname - 1 UNREACHABLE PARTNERS 
      IST2052I   ORIGIN NODE    PARTNER NODE    UNRCHTIM EXPIRES 
      IST2055I   origin_cpname  dest_cpname     1800s  07:54:10 
      IST314I   END

However, it appears that TRS is still selecting the unreachable path through the Enterprise Extender VRN because sessions continue to fail with sense code 08010000 following the unreachable partner messages that are received for additional dynamic PUs (for example, if the first INOP is for CNV00074, there can be additional INOPs for CNV00075, CNV00076, and so on).

The reason this is occurring is that these sessions were requested, and TRS selected the route through the EE VRN, before the first PU INOP and the detection of the unreachable partner. It can take a significant amount of time from the DIAL request until the timeout occurs. During this time, a number of sessions can be requested. A DISPLAY SESSIONS,LIST=ALL command will show the session status of the session for which a DIAL request is pending as ADIALIP. The session status of the other sessions waiting for this same path will show as PRAV3. Each of these pending sessions will fail. Further displays of the unreachable partner information will show that the EXPIRES time changes each time an INOP occurs.

This is normal processing for the EE connection network reachability awareness function. Any sessions that were pending before the INOP will fail. However, for any future sessions requested after the unreachable partner information is known, TRS will attempt to route around the EE VRN.