IMS Connect support for ISC TCP/IP communications

IMS Connect manages the TCP/IP connections and protocols for IMS when Intersystem Communication (ISC) parallel sessions use TCP/IP to link to IBM® CICS® Transaction Server for z/OS®.

The following figure shows the basic flow for a single ISC parallel session that uses TCP/IP. In the figure, the ISC TCP/IP terminal is defined dynamically in IMS by an ETO logon descriptor.

Figure 1. Overview of IMS Connect support for an ISC parallel session that uses TCP/IP
Begin figure description: The diagram shows three boxes: IMS, IMS Connect, and CICS. An ISC parallel is shown as a single two-way arrow between IMS and IMS Connect. In IMS Connect, the arrow points to a send port that in turn has an arrow that points to a CICS receive port. A return arrow from a CICS send port points to a receive port in IMS Connect, which in turn has an arrow that points back to the two-way arrow between IMS Connect and IMS. The boxes also contain the configuration statements required for each subsystem. End figure description.

Each ISC parallel session requires two sockets in IMS Connect: a send socket and a receive socket. CICS also requires two sockets for each ISC parallel session. An ISC link can support multiple ISC parallel sessions.

The ISC and RMTCICS statements, along with the CICSPORT keyword on the TCPIP statement, together define the TCP/IP connection from IMS Connect to IMS and from IMS Connect to CICS. These statements are defined in the IMS Connect configuration member in the IMS.PROCLIB data set.

Each TCP/IP socket provides a one-way path for transactions and reply data messages between IMS Connect and CICS. Acknowledgment messages (ACKs or NAKs) are sent on the socket connection from which the transaction or reply data message was received.

Communication between IMS Connect and IMS is enabled by the Structured Call Interface (SCI) of the IMS Common Service Layer (CSL).

ISC TCP/IP communication does not support RACF® PassTickets.

ISC messages between CICS and IMS cannot be modified or routed by any IMS Connect exit routines. The IMS Connect user message exit routines, such as HWSJAVA0, HWSSMPL0, or HWSSMPL1, are not used for ISC TCP/IP communication. The Port Message Edit exit routine is not supported.

ISC TCP/IP communication is supported by IMS type-2 commands. Only a limited number of IMS Connect WTOR and z/OS MODIFY commands, such as VIEWHWS and QUERY MEMBER, support ISC TCP/IP communication.

The IMS Connect Event Recorder exit routine (HWSTECL0) records events that are specific to ISC TCP/IP communications.