Containers used in the pipeline

A pipeline typically consists of a number of message handler programs and, when the CICS-supplied SOAP message handlers are used, a number of header processing programs. CICS® uses containers to pass information to and from these programs. The programs also use containers to communicate with other programs in the pipeline.

The CICS pipeline links to the message handlers and to the header processing programs using a channel with a number of containers. Some containers are optional, others are required by all message handlers, and others are used by some message handlers, and not by others.

Before a handler is invoked, some or all of the containers are populated with information which the handler can use to perform its work. The containers returned by the handler determine the subsequent processing, and are passed on to later handlers in the pipeline.

The containers can be categorized as:
Control containers
These are essential to the operation of the pipeline. Handlers can use the control containers to modify the sequence in which the handlers are processed. The names of the control containers are defined by CICS, and begin with the characters DFH.
Context containers
These contain information about the environment in which the handlers are called. CICS puts information in these containers before it invokes the first message handler, but, in some cases, the handlers are free to change the contents, or delete the containers. Changes to the context containers do not directly affect the sequence in which the handlers are invoked. The names of the context containers are defined by CICS, and begin with the charactersDFH.
Header processing program containers
These contain information that is used by header processing programs that are invoked from the CICS-supplied SOAP message handlers.
User containers
These contain information which one message handler needs to pass to another. The use of user containers is entirely a matter for the message handlers. You can choose your own names for these containers, but you must not use names that start with DFH.