Configuring support for communicating over a TCP/IP network

CICS® operating in a dual-mode environment uses both IPv4 and IPv6 networks and always attempts to communicate using IPv6 before using the IPv4 network. A single-mode environment operates in an IPv4 network only. You can set up TCP/IP services to use a number of CICS-supported protocols, including HTTP and IPIC.

Before you begin

You need a minimum level of CICS TS 4.1 to communicate using IPv6. The CICS region must be running in a dual-mode (IPv4 and IPv6) environment and the client or server with which CICS is communicating must also be running in a dual-mode environment. If a region is running in a single-mode (IPv4) environment or a region is operating at a pre-CICS TS 4.1 release, you can communicate using IPv4 only.

About this task

Follow these steps to configure your connection to use either IPv4 or IPv6 addressing, or a combination of the two formats.

Procedure

  1. Activate TCP/IP services by specifying TCPIP=YES as a system initialization parameter.
  2. Define resources to support the protocol you are using to communicate over in the TCP/IP network. Here are examples of two different protocols which can be defined using resources:
    1. If you are using IPIC, define and install a TCPIPSERVICE resource and an IPCONN resource in both partner regions.
      See Defining IP interconnectivity (IPIC) connections for examples and instructions to help you define and install your resource definitions.
    2. If you are using HTTP with CICS as an HTTP client, define and install a URIMAP resource in the issuing region and a TCPIPSERVICE resource in the listening region. Define the host name, IPv4 or IPv6 address that you want to use in the HOST attribute of the URIMAP(CLIENT) resource definition.
      See Creating a URIMAP resource for CICS as a HTTP client for information about URIMAP resources for HTTP requests.
  3. Optional: Advise your network administrator to define an IPv4 primary interface address to ensure that you do not have problems when communicating outside of a CICSplex. The primary interface address is the address that is specified in the PRIMARYINTERFACE statement for the TCPIP.PROFILE.
    If you issue a GETHOSTID call, GETHOSTID returns the IPv4 primary interface address, or the loopback address if GETHOSTID cannot find a host address. The IPRESOLVED option stores the address returned by GETHOSTID, so IPRESOLVED might contain either the primary interface address, or the loopback address. If you are communicating outside of the CICSplex, results can be unpredictable if a loopback address is returned. To define a primary interface address, see the information about the TCP/IP address space, PROFILE.TCPIP, in the z/OS Communications Server: IP Configuration Guide.

Results

The TCP/IP connection is correctly configured and is available for use over an IPv4 connection.

Your connection will also be available over IPv6 if you have the correct level of CICS and your environments have dual-mode capability.

What to do next

If you are having problems with your connection, see Dealing with TCP/IP connectivity problems.