IP interconnectivity (IPIC) overview

IPIC provides access to CICS® applications over the TCP/IP protocol, supporting both COMMAREA and CICS channel applications. COMMAREAs are limited to 32KB of application data, while CICS channels allow you to send and receive more than 32KB of application data in a single request.

Connections to CICS

IPIC communications between IBM® z/OS® Connect and CICS Transaction Server V4.1 (or later), use up to two sockets for each IPIC connection. If the IPIC connection is defined to use a maximum of one session, a single socket is used.

If one or more of the socket connections used for an IPIC connection ends unexpectedly, for example, because of a network error, all the sockets are closed and the IPIC connection is released.

Connection sessions

Each IPIC connection can be defined with up to 999 sessions. A single session handles a single request at a time and uses one CICS task, so the number of sessions determines the maximum number of simultaneous requests over an IPIC connection. The number of sessions is defined on the CICS server by the Receivecount parameter of the IPCONN definition and in IBM z/OS Connect by the sendSessions attribute of the zosconnect_cicsIpicConnection element in the server.xml configuration file. If the number of sessions differs on either side of the connection the actual number of sessions established is negotiated when the connection is established.

Setting session limits

The actual number of send sessions established depends on the values of the sendSessions and Receivecount attributes.

Table 1. How the number of simultaneous transactions over an IPIC connection is determined
zosconnect_cicsIpicConnection sendSessions value	IPCONN Receivecount value	Number of simultaneous transactions allowed
Set	Set (on IPCONN resource definition or customized autoinstall)	The lesser of the two values is used.
Set	Not set (default autoinstall)	The value of the IBM z/OS Connect `sendSessions` setting is used.
Not set	Set (on IPCONN resource definition or customized autoinstall)	The value of the CICS IPCONN `Receivecount` setting is used.
Not set	Not set (default autoinstall)	A value of 100 is used.

For more information about parameters for the zosconnect_cicsIpicConnection element, see Configuration elements in the Reference section.