Impact of having no paths in a class

In the XCF Activity Report - Usage by System, shown in Figure 1, the column labeled “ALL PATHS UNAVAIL” indicates the number of outbound message requests that were migrated to a signaling path in another transport class because there was no operational signaling path connected to the intended system and assigned to the selected transport class. A particular transport class could fail to have an operational signaling path for a particular system because:

There are no signaling paths assigned to that class that lead to the other system.
All the signaling paths assigned to that class that lead to the other system have temporarily or permanently failed.
All the signaling paths assigned to that class that lead to the remote system are incapable of transferring signals due to a "no buffer" condition.

When “ALL PATHS UNAVAIL” is not zero, there is interference between the transport classes. This means that the desired segregation of message traffic is not obtained. Generally, you want to avoid this condition by assigning signaling paths to the transport class that lead to the intended remote system. Messages migrated to an alternate signaling path incur additional overhead for XCF to select an alternate transport class. Furthermore, these messages can degrade the performance of messages sent in the transport classes that are chosen as alternates; particularly if the buffer size used by the alternate class is smaller than the buffer size required by the migrated message.

Thus “ALL PATHS UNAVAIL” can be an indicator of severe problems with the transport class definitions and/or the resources assigned to the class. For example, if the transport class did have signaling paths defined for the target system but none are working due to a "no buffer" condition, then it is a possible sympathy sickness indication.

However, the severity of the interference between classes must be considered in light of the number of message requests in the transport class as listed under "REQ OUT". If these messages occur relatively infrequently, it may not be worth providing a signaling path for their exclusive use.