IMS and IMS Connect high availability

When IMS assets serve as REST API endpoints through the IMS or IMS Database service provider, the first place to configure for IMS Connect high availability is in the Internet Protocol network that sends and receives messages.

When IMS assets are exposed as REST API endpoints when using the IMS or IMS Database service provider, the first step in configuring IMS Connect for high availability is to address the Internet Protocol (IP) network responsible for message transmission.

High availability for IMS Connect is typically implemented by using static or dynamic virtual IP addresses (VIPAs), or through Sysplex Distributor for TCP/IP-based load balancing and failover. A Sysplex Distributor directs incoming traffic for a given IP address to two z/OS® Connect Servers and two IMS Connect instances. The shared IP address and port that is used by the z/OS Connect Servers differ from those used by the IMS Connect instances. Each IMS Connect instance is configured to communicate with one or more IMS systems. Optionally, a Sysplex Distributor can be configured to prioritize local connections. For further details, refer to the Sysplex Distributor documentation.

Connections from z/OS Connect to IMS can be routed through a Sysplex Distributor-managed port that is shared across multiple IMS Connect instances to help ensure high availability.

The following diagram illustrates how connections between z/OS Connect Servers and IMS regions are established by using an existing IMS Connect high availability configuration. For simplicity, the image has two z/OS Connect instances. To avoid a single point of failure, it is recommended to deploy three or more z/OS Connect instances to avoid a single point of failure. This configuration allows one z/OS Connect instance to be taken offline, for example, for maintenance while maintaining full-service availability. The z/OS Connect Servers are configured to listen on shared port 5595 for incoming API requests. Each server defines an identical IMS connection configuration that targets IP address 192.0.2.1 on port 5595. The IMS connection itself is configured to use IP address 192.0.2.1 and port 5801. The Sysplex Distributor routes requests to this IP address across two IMS Connect instances that share port 5801. Each IMS Connect instance is configured to access one or more IMS systems. As noted earlier, a Sysplex Distributor can be configured to prefer local routing. For more information, see Sysplex Distributor.

Figure 1. A sample high availability configuration for connections to IMS from z/OS Connect
A sample high availability configuration for connections to IMS from z/OS Connect.
Note: The Sysplex Distributor in Figure 1 is shown as two separate boxes in the diagram for simplicity. There is only one Sysplex Distributor in the environment.

Shared resources in this configuration include:

  • Shared server configuration.
  • Shared archive files for services and APIs.
  • Shared IMS connection and interaction profiles.

For configuration steps related to shared resources, see Configure HA for connections to IBM z/OS Connect.