Location of failure in a route test

The variable text in message IST523I can help you determine which direction the route test was going when it failed. There are three possibilities. Either the failure is in the adjacent subarea or in the link from the adjacent subarea to the rejecting subarea; or the failure is in the rejecting subarea; or the location of the failure could not be determined. If the reason is "UNEXPECTED TYPE BYTE X'##'", then the location of the failure could not be determined. This condition should not occur.

If the reason is:

"A REQUIRED TG IS INACTIVE"
"MIGRATION ER NOT SUPPORTED"
"MIGRATION NODE DOES NOT SUPPORT THIS ER"
"MIGRATION NODE ENCOUNTERED"

the adjacent subarea follows the rejecting subarea in the route being tested. Therefore, the problem is in the adjacent subarea or the link to the adjacent subarea from the rejecting subarea. (See Figure 1)

Figure 1. Route test failure (TG inactive or migration)

Diagram that shows the possibilities of the location of the failure when the reason is TG inactive or migration.

If the reason is "ER NOT REVERSIBLE," "ER EXCEEDS MAXIMUM LENGTH," or "ER NOT DEFINED," the adjacent subarea precedes the rejecting node in the route being tested. (See Figure 2.)

Check to see whether the problem is a path definition error. If not, it might be a VTAM® error.

Figure 2. Route test failure (ER not reversible, exceeds maximum length, or not defined)

Diagram that shows the possibilities of the location of the failure when the reason is ER not reversible, exceeds maximum length, or not defined.

The ER MASK field indicates which ER numbers the rejecting subarea can use to send data back to the host that requested the test. (These explicit routes are called reverse explicit routes.) For example, an ER MASK field of hex 88 (binary 10001000) means that the 0 and 4 bits of the mask are turned on, so ER numbers 0 and 4 can be used to send data back to the host that requested the test. If message IST523I says an explicit route is "NOT REVERSIBLE," that means the rejecting subarea does not have the reverse explicit routes in its path definitions.

It is possible for the test results for an explicit route to be lost before they are displayed. For example, if a node or link along the explicit route fails between the time VTAM sends the test request and the time VTAM receives the test results, the results will be lost. If this occurs, reenter the DISPLAY ROUTE command for that explicit route.

See z/OS Communications Server: SNA Messages for complete explanations of the messages resulting from the DISPLAY ROUTE command.