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.