(1) .-HPRPSDLY--=--0--------. >>-+-----------------------+----------------------------------->< '-HPRPSDLY--=--ps_delay-'
- HPRPSDLY is meaningful only if VTAM® provides RTP-level HPR support.
Specifies the time that elapses before RTP pipes enter the path switch state.
The ARB flow control algorithm is sensitive to minor variations in the round-trip time and to unpredictable response times from the partner. This sensitivity might cause RTP endpoints to prematurely enter the path switch state. Although this situation does not affect availability, it does consume CPU cycles and also causes a significant number of path switch messages to be written to the console log.
The HPRPSDLY start option affects all RTP pipes with endpoints on this host. This start option affects only path switches that are the result of an unresponsive partner (path switches that generate the message IST1818I PATH SWITCH REASON: SHORT REQUEST RETRY LIMIT EXHAUSTED). The HPRPSDLY start option does not control path switches that are initiated as a result of a TG INOP, F RTP commands, or the PSRETRY function. If you do not code this operand, a ps_delay value of 0 is used.
- HPRPSDLY=ps_delay
- Specifies the minimum amount of time, in seconds, that local RTP endpoints must delay before entering the path switch state as the result of an unresponsive partner. During this time, the RTP endpoint periodically tries to contact the partner in an effort to avoid switching paths. The value 0 indicates that the RTP nodes will enter the path switch state when a predetermined number of retry attempts have been unsuccessful.
When RTP pipes are directly attached to Enterprise Extender (EE), you can specify the HPR path switch delay value at a more granular level. For predefined EE connections, define this parameter on the PU definition in the switched major node. For EE connection networks, define this parameter on the connection network GROUP definition statements in the EE XCA major node. For dial-in EE connections with associated PUs that are dynamically created, define this parameter on the model major node (DYNTYPE=EE) PU definition statement.
- This start option can be useful when the RTP partner is on a node that is CPU-constrained or is running in a virtualized environment. In both of these situations, allowing additional time for the RTP partner to respond might avoid unnecessary processing associated with a path switch.
- If alternate routes exist, specifying a long delay time might cause unnecessary delays for the sessions that are using RTP pipes to this host.
You can change the value of the HPRPSDLY operand with the MODIFY VTAMOPTS command while VTAM is running. The new HPRPSDLY value is used immediately by both new and existing RTP connections, if applicable.