When does the EE connection go away?

Because the EE connection is itself represented by a switched PU, you can code the DISCNT operand to disconnect the EE switched PU. If DISCNT=YES is coded, the disconnect time used is that specified on the VTAM® start option DISCNTIM (default is 15 seconds). Alternatively, you can specify DISCNT=(DELAY,,s) on an EE PU where s is equal to the number of seconds to be used for the disconnect time.

Because the EE PU (unlike RTP PUs) has no sessions queued directly to it, the disconnect decision is based on a period of inactivity rather than the termination of the last session.

If RTP's ALIVE timer is set to half of the disconnect time, RTP status messages (keep-alive flows) will keep the PU from dropping as long as at least one RTP is using the EE PU.

The Logical Data Link Control (LDLC) layer monitors the EE connection, and terminates the EE connection if contact is lost with the partner. The LDLC inactivity trigger is controlled by three parameters on the PORT or GROUP statements:

LIVTIME - The amount of inactivity time that can lapse before LDLC tests the connection
SRQTIME - The amount of time LDLC waits for a response to its test
SRQRETRY - The number of times the test is retried

The connection is terminated if no activity or response occurs when using the following formula:

LIVTIME + ((SRQRETRY+1) * SRQTIME) seconds

This is an approximate formula. The actual duration of the LDLC layer outage detection window should be within plus or minus one LIVTIME interval of the calculated amount.

Guidelines:

Lengthen the HPR path switch timers (HPRPST) as necessary to ensure that all four timers are longer than the LDLC timeout interval. This ensures that RTP pipes stay in path switch long enough during IP network instability for the EE link to disconnect, and enables another path to be selected.
- Alternatively, specify HPRPSDLY=EEDELAY on the definition statements that represent EE connections. The HPRPSDLY parameter is available on the PU definition statement in the switched and model (DYNTYPE=EE) major nodes, and also on the connection network GROUP definition statements in the EE XCA major node. For more information about the HPRPSDLY parameter, see z/OS Communications Server: SNA Resource Definition Reference.
When possible, ensure that the values of the LDLC parameters are consistent between the endpoints of the connection. If the EE partner is not a z/OS® endpoint, see that product's documentation for details on setting its LDLC parameters.
For predefined EE PUs, specify DISCNT=NO.

Tip: The LIVTIME, SRQTIME, and SRQRETRY parameters are customer-configurable parameters that control the ability of the LDLC-layer to detect TCP/IP network connectivity problems; these parameters should not be confused with the similarly-named variables associated with HPR's Adaptive Rate-Based congestion control (ARB) algorithm that is used to monitor each RTP connection. Each RTP has associated with it a liveness timer, a short request timer, and a short request retry counter. However, the RTP values are algorithmically maintained, are not configurable, and are independent of the LDLC parameters. (It is possible to influence the RTP’s liveness timer value by coding DISCNT=YES for the connections used by the RTP.)

See the SRQRETRY description in topic in z/OS Communications Server: SNA Resource Definition Reference for more information.