Explanation
This message is the first in a group of messages
that VTAM® issues when an optimal
CNN route exists and is not chosen during session activation. A complete
description of the message group follows the example.
IST1774I OPTIMAL CNN ROUTE NOT CHOSEN - ENTRY/EXIT SUBAREA MISMATCH
IST1775I CNN ENTRY SUBAREA = entry_subarea CNN EXIT SUBAREA = exit_subarea
IST664I REAL OLU=luname1 REAL DLU=luname2
IST889I SID = session_id
IST314I END
IST664I - The origin LU may be either the PLU or SLU. The same applies
for the destination LU. If the origin or destination LU name is unknown, VTAM displays ***NA***.
IST889I - sessid is a unique identifier for the session.
If the session ID is unknown, VTAM displays
***NA***.
IST1774I - A CNN Route is not optimal if the following conditions are both
true:
- The chosen CNN entry and exit TG subareas do not match.
- Another active TG to the network node is found that has the same
characteristics as the chosen entry TG and the same subarea as the
CNN exit TG.
- The reason a nonoptimal route might be chosen is one of the following:
- The topology of the CNN is not known by the APPN topology and
route selection process.
- The route was calculated by a non-VTAM node that does not support
the use of subarea numbers in route calculation.
- The following figure is an example of a configuration:
Figure 1. Sample configuration
- In this figure, the CNN is composed of VTAM2, NCP1, and NCP2.
The subarea of NCP1 is the CNN entry TG subarea and the subarea of
NCP2 is the CNN exit TG subarea. A session is started between APPL1
(PLU) and LU2 (SLU). If the adjacent network node (NN1) chooses to
use TG1 instead of TG2, then the IST1774I message group will appear
on VTAM2.
Note: The APPN node that picked the CNN entry TG (NN1 in
the above configuration) is the NNS of the PLU, which may or may not
be a VTAM. In addition, the
NNS of the PLU may or may not be directly adjacent to the CNN.
IST1775I - This message follows IST1774I and indicates the CNN entry subarea
and the CNN exit subarea.
- entry_subarea is the decimal subarea of the
node in the CNN where the BIND entered the CNN from the PLU.
- exit_subarea is the decimal subarea of the
node in the CNN where the BIND exited the CNN to the SLU.
System action
Operator response
Save the system log for problem determination.
System programmer response
If the APPN node calculating the
session route (choosing the CNN entry subarea) was not VTAM, then change the APPN TG characteristics.
If the APPN node calculating the session route (choosing the CNN
entry subarea) was pre-V2R7 VTAM and
the session partner is an LU on the CNN exit subarea (NCP), then change
the APPN TG characteristics. See the z/OS Communications Server: SNA Network Implementation
Guide for more information about APPN TG characteristics.
If the APPN node calculating the session route is, at a minimum,
V2R7 VTAM, then request a dump
of the VTAM calculating the
session route for problem determination. CNNRTMSG=SUPPRESS may be
specified as the start option value or modified with the MODIFY VTAMOPTS
command to suppress message group IST1774I.
Routing code
Descriptor code