GDDM V3R2 Base Application Programming Guide
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CICS pseudoconversational applications

GDDM V3R2 Base Application Programming Guide
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If a conversational application is widely used, under CICS this could adversely affect overall system performance.
For this reason, CICS provides pseudoconversational support, in which a series of nonconversational transactions gives the appearance to the terminal user of a single conversational transaction.
The pseudoconversational version of the application outlined in "CICS conversational applications" in topic E.2 is as follows:
  1. Start the application
  2. If first invocation
    Then perform initialization
    Else
    • Receive the terminal input
    • Process the input
  3. If finish not requested
    Then send data to the terminal (typically, display panel)
    Return to CICS requesting reinvocation of transaction
    Else Return to CICS
As you can see, the conversation is implemented as discrete send and receive calls, and while terminal input is being awaited, no transaction exists. CICS takes care of reading the input when the user enters it, and then starts a transaction to process it.
There are a number of considerations affecting the choice of conversational or pseudoconversational programming for a particular application-the amount of usage, and file integrity across transactions being examples.
Information about these and other considerations affecting application design under CICS can be found in the CICS Application Programming Guide.
A CICS pseudoconversational application appears to the terminal user as a normal conversational transaction, but is, in fact, a series of separate transactions where the CONVERSE is implemented as SEND and RECEIVE. One transaction ends with a SEND, and the next starts with a RECEIVE.
In this way, system resources can be released for the duration of "operator think time" thus making more efficient use of CICS.
GDDM provides pseudoconversational support for all types of alphanumeric data, for output-only graphics and images, and for partitions by means of a strictly defined protocol for GDDM application call sequences.
You can find an example of a CICS pseudoconversational transaction in "A CICS pseudoconversational programming example" in topic 23.6.
GDDM provides two modes of pseudoconversation:
  • Transaction-dependent mode
  • Transaction-independent mode.

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