CPI Communications driven application programs

CPI Communications driven application programs are defined only in the APPC/MVS™ TP_Profile data set; they are not defined to IMS.

The CPI Communications driven application program definition is dynamically built by IMS when a transaction is presented for scheduling by APPC/MVS based on the APPC/MVS TP_Profile definition after IMS restart. The definition is keyed by TP name. APPC/MVS manages the TP_Profile information.

When a CPI Communications driven transaction program requests a PSB, the PSB must already be defined to IMS by using the APPLCTN macro during system definition and by generating the appropriate PSBs and ACBs with the Program Specification Block (PSB) generation utility and the Application Control Blocks Maintenance utility when APPLCTN PSB= is specified. When APPLCTN GPSB= is specified, generating PSBs and ACBs is not required.

CPI Communications driven application programs must use CPI Communications calls to accept the incoming conversation and to send a reply on the same conversation. The DL/I GU call is not used to retrieve the initiating transaction from the LU 6.2 application program. No IMS resources are allocated when the application program is scheduled. Instead, the application program can use the DL/I APSB call to allocate a PSB that provides access to IMS databases and to alternate PCBs. A CPI Communications driven application program can send messages to other terminals (either LU 6.2 or non-LU 6.2) or other IMS transactions (either local or remote) by inserting to an alternate PCB, after allocating the appropriate PSB. Both the explicit and implicit API can be used on the same application program.

IMS provides the following services for CPI Communications driven application programs:
  • Schedules the transaction.

    IMS does not receive input before scheduling. It does not interact with the conversation at any time other than to possibly reject the inbound allocate request. If IMS rejects the inbound allocate request, the transaction is not scheduled.

  • Provides sync point of local resources.
  • Schedules PSB if called by application program.
  • Processes calls to alternate or database PCB made by the application program.