Configuring a shared-queues environment

You can configure a shared-queue environment by using either a cloned configuration or a partitioned configuration.

Figure 1 and Figure 2 illustrate two methods of configuring a shared-queues environment.

Cloned configuration

A cloned configuration involves creating identical IMS systems, with almost identical system definitions. Some differences in the definitions are required, such as MSC links. You can override the MTO definitions generated during system definition in IMS PROCLIB member data set DFSDCxxx.

Related reading: For more information on overriding the MTO definitions, see IMS Version 15.3 System Definition.

The LTERMs, databases, and transactions for all the IMS systems are defined identically. In this configuration, any IMS is able to process a particular transaction. Cloned configurations are useful for automatic workload balancing.

Recommendation: To take full advantage of a cloned configuration, ensure that the databases are shared across the IMSplex.
Figure 1. Cloned configuration in a shared-queues environment
Begin figure description: Three IMS systems have the same LTERM and transaction definitions. They share databases and message queues. They each have their own MTO. End figure description.

Partitioned configuration

A partitioned configuration separates the VTAM® network responsibilities from the database work. Each resource is defined to only one IMS.

You can define an ES/9000 9021 to manage the VTAM network as an IMS front end, while multiple smaller 9672 CMOS processors manage the database work.

Partitioned configurations are useful as replacements for, or additions to, MSC networks.

In the partitioned configuration in the following figure, IMS A acts as the front end, and has LTERM 1, LTERM 2, and MTO 1 defined. IMS B, IMS C, and IMS D act as back ends, each with separate transactions and databases defined. Transactions in this configuration can run only on the IMS systems on which they are defined.

Figure 2. Partitioned configuration in a shared-queues environment
Begin figure description. Three back-end IMS systems have different databases and transactions. One front-end IMS has LTERM definitions. All IMS systems share a message queue and have their own CQS and MTO. End figure description.