gtps2m1zACF/SNA Data Communications Reference

CP-CP Session Failures

If the CP-CP sessions are not active, no new APPN LU-LU sessions can be started. No new HPR LU-LU sessions can be started either. If CP-CP sessions are active and then break for any reason, active LU-LU sessions (APPN and HPR) are not affected; they remain active.

With HPR support, the CP-CP sessions are not only used for starting LU-LU sessions, but also are involved in the path switch process. If CP-CP sessions are not active, it is not possible to perform a path switch on an RTP connection. If the TPF system detects a failure in the route of an RTP connection, but the CP-CP sessions are not active, the path switch timer is started for that RTP connection. If the CP-CP sessions are activated before the path switch timer expires, the TPF system will begin the path switch process by sending a LOCATE request on the CP-CP sessions. However, if CP-CP sessions are never activated and the path switch timer expires, the RTP connection is cleaned up.

Activation of CP-CP sessions not only starts the path switch process for RTP connections that are in SWITCHING state, but will restart the path switch process if necessary. For example, the TPF system sends a LOCATE request to start the path switch process for an RTP connection, but the CP-CP sessions fail before the LOCATE reply is received. If the CP-CP sessions are reactivated before the path switch timer expires, the TPF system will send another LOCATE request to restart the path switch process.