.-LIVTIME--=--(10,0)------------------. >>-+-------------------------------------+--------------------->< '-LIVTIME--=--(init_value, max_value)-'
| statements: | PORT, GROUP |
| dependencies: | MEDIUM=HPRIP |
| range: | init_value 5-25 max_value 0 or init_value-3600 |
Specifies the Enterprise Extender logical data link control liveness timer interval range, in seconds.
There are two timer functions that affect Enterprise Extender connections: the logical data link control (LDLC) timer and the disconnect timer. The operands that control the LDLC timer that are specified on the PORT and GROUP macros are LIVTIME, SRQTIME, and SRQRETRY. The disconnect timer is controlled by the DISCNT keyword on the PU macro.
LDLC uses the LDLC timer interval to determine how long to wait before considering an Enterprise Extender connection inoperative. Two values can be specified on the LDLC liveness timer (LIVTIME). These values are optional with the first being the initial LIVTIME value (init_value) and the second the maximum LIVTIME value (max_value). If the max_value is specified or defaulted to 0, or the max_value is specified as equal to the init_value, the LDLC timer facility uses the initial value for the liveness timer.
During periods of inactivity on the Enterprise Extender connection, when the liveness timer expires, LDLC polls the partner with an LDLC TEST request. This verifies that the EE partner is still available. In Enterprise Extender configurations that experience long periods of inactivity, the LDLC TEST flows or HPR status flows might be the only flows occurring. In configurations involving large numbers of EE connections, reducing these flows can significantly reduce EE overhead (CPU consumption).
Specifying a max_value larger than the init_value enables the EE LDLC Keep-Alive Reduction Function. This function enables the current LIVTIME window to expand and contract based on current network conditions. Expanding the current LIVTIME window reduces the number of LDLC test flows that occur during periods of inactivity.
- The current LIVTIME interval is always initialized to the init_value when the connection is established.
- During a specific LIVTIME interval, if the only activity over the EE connection are LDLC TEST flows, the current LIVTIME value is doubled in size. The current LIVTIME value can double in size up to the size specified by max_value . This guarantees that VTAM® will poll the EE partner at least once every number of seconds specified by the max_value value.
- When HPR traffic starts flowing over an inactive EE connection
and the current LIVTIME window has expanded to be larger than the
initial value, VTAM immediately
resets the LIVTIME value to the initial value and begins testing the
EE connection for connectivity.
Result: When the EE LDLC Keep-Alive Reduction Function is enabled, there is a trade-off between CPU reduction and Enterprise Extender's responsiveness to TCP/IP connectivity problems. EE will verify the TCP/IP connection to the partner when HPR traffic resumes. However, if the EE partner is no longer reachable, there is an LDLC disconnect timeout period before the EE connection is disconnected. These trade-offs must be taken into account when selecting a max_value value for the LIVTIME facility.
The disconnect timer works independently of the LDLC timer, and determines the time interval during which Enterprise Extender monitors for data transfer before disconnecting the link (if no data transfer occurs).
- The interval determined by LIVTIME + (SRQTIME*(SRQRETRY+1)) expires if required signal responses are not received.
- The DELAY value specified by DISCNT expires if no data transfer occurs.