The LDLC layer monitors the EE connection, sending a test frame if no activity is detected for the number of seconds specified by the LIVTIME operand as coded (or defaulted) on the XCA PORT statement. If no response is received for the number of seconds specified by the SRQTIME operand, another test frame will be issued. As long as no response is received, LDLC will retry SRQRETRY + 1 times. If no response is received after LDLC tries again the last time, the EE link will be disconnected.

z/OS Communications Server provides the EE switched PUs disconnect time value to each RTP, and the RTP sets its liveness timer (which is independent from the LDLC liveness timer associated with the LIVTIME parameter) to half of the disconnect value, or 3 minutes, whichever is smaller. This ensures that as long as an RTP connection is actively associated with that EE switched PU, it sends status messages (generated when the liveness timer pops) often enough to keep the PU from disconnecting because of inactivity, even if there is a lull in data traffic using the RTP connection.

At yet a higher layer, the RTP connection is itself represented by a switched PU that, by default, looks like a PU with DISCNT=YES and a 10 second DISCNTIM value. Therefore, by default the RTP PU will disconnect itself if its last session goes away, and no new session is queued to it for a period of 10 seconds. If a different DISCNTIM value is required for the RTP PU, or if DISCNT=NO behavior is required (meaning the RTP PU will not disconnect until forced down by lack of connectivity, partner deactivation, or operator command), then you can code a model PU, DYNTYPE=RTP.