COMMAREA and channels, are not they same?

[GGarung]

Hi,

I have basic knowledge about CICS and have seen program using COMMAREA. Concept of Channels is new to me. I think , are not COMMAREA and channels just same. Channels just provide more flexibility/relief from the COMMAREA maximum size of 32766 bytes? Or is there more application of channels? Please guide me.

[Robert Sample]

There is a Redbook, SG24-7227, Using IBM CICS Transaction Server Channels and Containers which you should read. From this Redbook:

A container is a named reference to a storage area managed by CICS that can
hold any form of application data. A container can be any size, and can hold data
in any format that the application requires. An application can reference any
number of containers. CICS provides EXEC API verbs to create, delete, reference,
access, and manipulate a container, and to associate it with a channel.

A channel is a uniquely named reference to a collection of containers. A channel
is analogous to a COMMAREA, but it does not have the constraints of a
COMMAREA. CICS provides an EXEC API, which associates a named channel
with a collection of one or more containers.

This is an easy way of grouping parameter data structures that might pass to a
called application. CICS deletes a channel and its containers when it can no
longer be referenced (when a channel becomes out of scope).

A COMMAREA is not named (other than being called DFHCOMMAREA), so right there is the first difference between COMMAREA and channels. Also note that channels require you to reference containers -- another difference already.