.-UNRCHTIM--=--value_of_unrchtim_start_option_value1-. >>-+----------------------------------------------------+------>< '-UNRCHTIM--=--unreachable_time----------------------'
| statements: | PORT, GROUP |
| dependencies: | Enterprise Extender connections; VNNAME or VNTYPE |
| range: | 0, or 10–65535 |
Specifies the default number of seconds that a partner node for a session path through an Enterprise Extender connection network is considered unreachable after certain Enterprise Extender connection network failures. During this period, the path through the Enterprise Extender connection network to this partner node will not be considered for new sessions or HPR path switches. A partner node is determined to be unreachable when a dial failure occurs across an Enterprise Extender connection network or when an INOP of an existing connection through an Enterprise Extender connection network is detected. UNRCHTIM is meaningful only if the NODETYPE start option is also used.
Guidelines:
- Coding UNRCHTIM for an Enterprise Extender connection network provides a way to route new sessions and HPR path switches around a problem with a specific connection network path, as long as an alternate route exists, until the underlying problem can be resolved. Specifying UNRCHTIM=0, or allowing it to default, will cause Enterprise Extender connection network processing to work the same as it does in z/OS® V1R5 Communications Server and prior releases, but the topology and routing services component will not be informed of Enterprise Extender connection network connectivity problems and will continue to use the connection network path for new sessions and HPR path switches even if alternate paths are available. These new sessions and HPR path switches will continue to fail until the underlying problem is resolved. See z/OS Communications Server: SNA Network Implementation Guide for additional information about the implications of turning on UNRCHTIM for an Enterprise Extender connection network.
- Although an Enterprise Extender connection network, including the virtual node name, type, and all TG characteristics, can be defined on the PORT definition statement, you should define your Enterprise Extender connection network on the corresponding GROUP definition statement instead. By coding all connection network and TG characteristics operands on the GROUP statement, the VNGROUP operand is no longer needed. Also, because there can be multiple connection networks defined in an Enterprise Extender XCA major node with multiple GROUP definition statements, defining all of the operands on the GROUP statement to which they apply provides more clarity.
Tips:
- The unreachable_time value should be the same for all PORT or GROUP statements that define the same connection network. You can code a PORT statement and multiple GROUP statements with the same VNNAME if different IP addresses are specified. This allows you to have multiple TGs to that connection network. If the unreachable_time values are different on these statements, the unreachable_time value used will be the value associated with the line on which a dial failure or connection INOP occurs, causing the unreachable time to be unpredictable.
- An end node that has detected an unreachable partner path notifies its network node server (NNS) of the unreachability so that the NNS can use that information when calculating routes for the end node. Beginning with z/OS V1R8 Communications Server, the NNS overrides the unreachable_time value sent by the EN using its unreachable time value for the associated connection network, if configured, or the value specified in its UNRCHTIM VTAM® start option. With this enhancement, changing the unreachable time value for an Enterprise Extender connection network no longer requires you to update every attached end node. Only the attached network nodes and those attached end nodes with NNS running z/OS V1R6 or V1R7 Communications Server need to be updated with the new value. You must still configure an unreachable time value on every end node to activate the EE connection network reachability awareness function.