Intercommunication using IP interconnectivity

IPIC connection requirements

You must activate TCP/IP services in each CICS region that you are connecting before you create your IPIC connection.

The IPIC connection consists of two complementary resources, an IPCONN definition, and a TCPIPSERVICE definition, which you must install in each CICS region that you are connecting. The IPCONN definition is the CICS resource that represents the outbound TCP/IP communication link, and the term IPCONN is commonly used to refer to an IPIC connection. The inbound attributes of the connection are specified by the TCPIPSERVICE definition. The TCPIPSERVICE resource is named in the TCPIPSERVICE option of the IPCONN definition.

Figure 1 shows the relationship between IPCONN and TCPIPSERVICE definitions.

Synchronization levels

IPIC connections support synchronization level 2; that is, they support full CICS sync pointing, including rollback.

Socket capacity

For CICS TS 4.1 systems and later, up to two sockets are available for IPIC communications. For connections to CICS TS 3.2 systems, only one socket is available for IPIC communications. If you lose one or more of the sockets that are in use by an IPCONN, for example because of a network error, all the sockets are lost and the IPCONN is released.

CICS IPIC heartbeat function

The CICS IPIC heartbeat function discovers and reports connectivity problems with idle connections by sending a heartbeat message over a connection during periods when no other messages are being transmitted. Before the introduction of the CICS IPIC heartbeat, connectivity problems with an idle connection remained unnoticed until an attempt was made to send a new message over the connection.

The CICS IPIC heartbeat also maintains a connection that might pass through one or more firewalls. If the CICS IPIC heartbeat is not used, the connection can time out because of lack of usage.

The CISP task checks all the IPCONN resources at intervals of approximately 60 seconds. A CIS1 task is attached to resources that are acquired, and are then connected to a CICS region that can accept a heartbeat message, and have received no message traffic since the end of the previous interval.

If the heartbeat message is sent and a response is not received within 10 seconds, a second message is sent. If a response to the heartbeat message is not received within a further 10 seconds, the connection is put into a released state. If a heartbeat message cannot be sent because the connection is no longer usable, an error message is issued and the connection is released automatically.

CICS IPIC heartbeat messages are only sent by CICS TS V5.1 regions or higher, however, they can received by older releases of CICS TS at V4.1 or higher. The heartbeat messages cannot be sent to any version of CICS Transaction Gateway or TXSeries.