Planning for conversational processing

Conversational processing is available to terminals that are attached to any IMS in an MSC network to the same extent as if they were in a single-system environment.

The following differences apply to conversational processing in an MSC network:
  • All transactions used in a conversation must be defined as conversational in each IMS of the MSC network.
  • The input system controls the conversational resources for the duration of the conversation. When the input system receives a conversational transaction, it inserts the scratchpad area (SPA) as the first message segment, and routes the message to the destination application program.
  • Any system in the MSC network can process any step in the conversation.
  • Program-to-program switches can be routed from system to system.
  • SPAs that are used in multisystem conversations must follow these rules:
    • For the SPA ISRT, conversational program-to-program switches can occur to a transaction with a SPA that is equal, larger, or smaller in size.
    • The minimum size of a SPA is 16 bytes (X'10'), and the maximum size is 32767 bytes (X'7FFF').

Generally, terminal operators and application programs are unaware of whether a conversation is multisystem.

Exceptions:
  • Suppose a conversational program inserts a message to a response alternate PCB in a remote system. By implication, this destination is in the input system and is verified by the input system. Destination verification in this case involves confirming that the specified logical terminal is still assigned to the input terminal. If the logical terminal has been reassigned, the input system activates the Conversation Abnormal Termination exit routine, and terminates the conversation. The status code that is returned to the application program is blank, indicating success. This status code is blank even when the actual result is unsuccessful due to the condition described.
  • Suppose an application program executing in a system other than the input system uses the SPA to specify a transaction code, thereby passing conversation control to another program. If the specified transaction code is invalid, the input system activates the Conversation Abnormal Termination exit routine, and terminates the conversation. No status code is returned to the application program.
MSC support for APPC/IMS and OTMA includes the following IMS transaction types:
  • Conversational
  • Nonconversational
  • Response mode
  • Non-response mode
Restriction: MSC does not support Fast Path.