Messages IST1774I and IST1775I received during LU-LU session activation

Problem statement

LU-LU session activation completes successfully with the issuance of messages IST1774I, IST1775I, IST664I, IST889I, and IST314I at the composite network node (CNN).

Common symptoms

The following messages are received:

IST1774I OPTIMAL CNN ROUTE NOT CHOSEN - ENTRY/EXIT SUBAREA MISMATCH
IST1775I CNN ENTRY SUBAREA = subarea   CNN EXIT SUBAREA = subarea
IST664I REAL  OLU=luname       REAL  DLU=luname
IST889I SID = sessid
IST314I END

Probable cause

An optimal CNN route exists and was not chosen during session activation. Non-optimal routes might result because the topology of the CNN is not known by the APPN topology and route selection process, or because the route was calculated by a non-VTAM node that does not support the use of subarea numbers in route calculation.

User response

Change the APPN TG characteristics. For more information about APPN TG characteristics, See the z/OS Communications Server: SNA Network Implementation Guide.

To suppress message group IST1774I, CNNRTMSG=SUPPRESS can be specified as the start option value or modified with the MODIFY VTAMOPTS command.