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How do I set MaxWorker and MaxConnect when configuring CICS TG in Local Mode under WebSphere?

Question & Answer


Question

I need to limit the number of EXCI threads WebSphere uses to connect to CICS TS. When CICS TG runs as a separate address space (remote mode) I can do this by setting MaxWorker. But when I run CICS TG in Local Mode there is no ctg.ini. How do I set MaxThreads and MaxWorkers?

Answer

When CICS TG functions in 'local' mode under WebSphere, MaxThreads and MaxWorkers do not apply.

The parameters specified in ctg.ini or on the command line when starting the gateway daemon (address space) do not apply when the CICS TG functions are being used in 'local mode' by applications. Rather, the CICS TG functions are used directly from the client application's runtime.

In the case of a client application in WebSphere, there are no CICS TG threads at all in the WebSphere address space. Therefore, there are no CICS TG Connection Manager threads or Worker threads. Since these things don't exist, the CTG.INI parameters MaxThreads and MaxWorkers do not apply.

Any threads which exist in the WebSphere runtime are those managed by the application server and are either created by WebSphere for its own use or perhaps created by the application code if it spawns additional threads. (Multi-threaded applications are discouraged in WebSphere, but that may not be an absolute restriction.) The CICS TG functions are invoked from the CICS TG classes and run attached to the application threads. Therefore, EXCI pipes which carry requests and data in z/OS to the CICS address space(s) are attached to the application threads.

Without these settings in a WebSphere z/OS environment, it is possible to exhaust the EXCI pipe capacity of a single address space. This can easily happen if the applications instantiate the JavaGateway object in the doGet or doPost method of a servlet. If you have exhausted the EXCI pipe capacity, your servlets will receive an error during execution indicating that CICS is unavailable. This can be avoided by setting the environment var CTG_PIPE_REUSE=ONE.

This, and other CICS TG variables can be set in WebSphere:

CICS TG Environment Variables: Local and Remote Mode

Configuring a Local Mode Topology

Another way to avoid exceeding the EXCI pipe limit in local mode is to reduce the size of the connection pools in the application server(s).

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Product Synonym

CICSTG CICS TG

Document Information

Modified date:
23 January 2015

UID

dwa1166673