Dynamic routing of BTS activities

Within a BTS-set, your BTS processes and activities can be routed dynamically across the participating regions.

Note that BTS routing is at the activation level; for example, within the same process, different activations of the same activity may execute on different regions. When an event is signalled, the relevant activity is activated in the most appropriate region in the BTS-set, based on one or more of the following:

Which BTS activities can be dynamically routed?

Not all activations of BTS processes and activities can be routed.

Processes and activities that are activated asynchronously with the requestor--by means of a RUN ASYNCHRONOUS command--can be routed either dynamically or statically.

Processes and activities that are activated synchronously with the requestor--by means of a RUN SYNCHRONOUS or LINK command--are always run locally. They cannot be routed, neither dynamically nor statically. A RUN SYNCHRONOUS or LINK command issued against an activity whose associated transaction is defined as DYNAMIC(YES), or as remote, results in the activity being run locally. (When an activity is activated by a LINK command, all the attributes of its associated transaction are ignored, because the activity runs under its parent’s TRANSID--there is no context-switch.)

Thus, to be eligible for dynamic routing:

"Daisy-chaining" is not supported. That is, once a BTS process or activity has been routed to a target region it cannot be re-routed from the target to a third region, even though its associated transaction is defined as DYNAMIC(YES) in the target.

Understanding distributed routing

CICS has two dynamic routing models--the "hub routing model" and the distributed routing model. Likewise, there are two user-replaceable sample routing programs--the dynamic routing program, DFHDYP, which implements the "hub" model, and the distributed routing program, DFHDSRP, which implements the distributed model. Both models and their associated routing programs are described in detail in the CICS Intercommunication Guide.

The CICSPlex® SM routing program, EYU9XLOP, can be used with either routing model--that is, it can function as either a dynamic routing program, a distributed routing program, or both.

BTS routing uses the distributed routing model. It is important to understand how this differs from the traditional "hub" model.

The hub model

The "hub" is the model that has traditionally been used with CICS dynamic transaction routing. A dynamic routing program running in a terminal-owning region (TOR) routes transactions between several application-owning regions (AORs). Usually, the AORs (unless they are AOR/TORs) do no dynamic routing. Figure 51 shows a "hub" routing model.

Figure 51. Dynamic routing using a hub routing model. One routing region (the TOR) selects between several target regions.
 The picture shows a terminal-owning region (TOR) connected to four application-owning regions (AORs). A dynamic routing program runs in the TOR and balances transaction requests across the AORs. The TOR is both the requesting region and the routing region. Each of the AORs is a possible target region.

The "hub" model applies to the routing of:

The "hub" model is a hierarchical system--routing is controlled by one region (the TOR); normally, a routing program runs only in the TOR.

Advantage of the hub model

It is a relatively simple model to implement. For example, compared to the distributed model, there are few inter-region connections to maintain.

Disadvantages of the hub model

The distributed model

In the distributed model used for BTS routing, each participating CICS region may be both a routing region and a target region. A distributed routing program runs in each region. Figure 52 shows a distributed routing model.

Figure 52. Dynamic routing using a distributed routing model. Each region may be both a routing region and a target region.
 The picture shows four CICS regions. Each region is connected to all the other regions. A distributed routing program runs in each region. Each region may be a requesting region, routing region, or target region. It is a peer-to-peer model.

The distributed model applies to the routing of:

The distributed model is a peer-to-peer system--each participating CICS region may be both a routing region and a target region. A distributed routing program runs in each region.

Advantage of the distributed model

There is no single point-of-failure.

Disadvantages of the distributed model

Controlling BTS dynamic routing

You can control the dynamic routing of your BTS activities by either of the following means:

  1. Writing your own CICS distributed routing program--see Using a CICS distributed routing program.
  2. Using the CICSPlex System Manager (CICSPlex SM) product to:

    See Using CICSPlex SM with BTS.

Related concepts
The scope of a BTS-set
Sysplex support in BTS
Related tasks
Creating a BTS-set
Using a CICS distributed routing program
Using CICSPlex SM with BTS
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