Introduction to channels and containers

Channels and containers provide a method of transferring data between CICS® programs, in amounts that exceed the 32 KB limit that applies to communication areas (COMMAREAs).

Each container is a named block of binary (BIT) or character (CHAR) data that is not limited to 32 KB. Containers are grouped together in sets called channels.

The channel and container model has several advantages over the communication areas (COMMAREAs) used by CICS programs to exchange data:
  • Unlike COMMAREAs, channels are not limited in size. Any number of containers can be added to a channel, and the size of individual containers is limited only by the amount of storage that you have available. Consider the amount of storage available to other applications when you create large containers.
  • Because a channel can consist of multiple containers, it can be used to pass data in a more structured way, allowing you to partition your data into logical entities. In contrast, a COMMAREA is a monolithic block of data.
  • Unlike COMMAREAs, channels do not require the programs that use them to keep track of the size of the data.
  • CICS automatically destroys containers and their storage when they are no longer required.
When you are using channels and containers in preference to COMMAREAs, note that:
  • A channel can use more storage than a COMMAREA to pass the same data.
  • Container data can be held in more than one place.
  • COMMAREAs are accessed by pointer, whereas the data in containers is copied between programs.
For more information about using channels and containers see the following topics: