The need for passing data more than the conventional 32K arise from the fact that modern CICS programs now should have the ability to interface with applications outside the bounds of the CICS and process large quantities of data in XML(Extensible Markup Language) and JSON (JavaScript Object Notation) formats.These formats are used to transfer large binary objects, such as images, in addition to traditional character and numeric data.Execute Interface Block or DHFEIBLK is a control block which is loaded automatically by CICS for every program, EIB is unique to a task and contains a set of system related information corresponding to the task.
![]() One of the most frequently used fields from the EIB block is EIBCALEN, this half word binary field holds the length of COMMAREA. Data can be written to a TSQ or VSAM file and the name can be passed through COMMAREA or MQ but this would involve allocation of program-specific managed resources and would require implementing the resource setup and configuration, introducing extra processing. The receiving program can access the data using the correct Channel and container name. A subsequent PUT command using the same Channel and Container name will replace the data. When these programs end, CICS automatically deletes the containers and their storage. If a program is not invoked using a Channel, then it does not have a current channel. For example in the receiving program above, if the GET and PUT commands do not include the Channel name, then the current channel name (the channel with which the program was invoked) of EMP-CHNL is assumed by CICS. A call is treated more or less like an extended PERFORM statement. If the name supplied has fewer than 16 characters, it is padded with trailing blanks. CICS automatically takes care of assigning of channel and container names to the respective tasks. Dfhcommarea In Cobol Program Driver By EitherA program can even be written to be driver by either COMMAREA or channels and containers. If you see no reason to pass data beyond 32K or there is no need to have multiple data structures, COMMAREA should work just fine. If you have a need to interface with applications outside the bounds of the CICS and process large quantities of data then channels and containers structure is the way to go. Hope this helped you get a basic overview of CICS channels and containers.
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