CPI-C 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. Their 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 through the APPLCTN macro for system definition and through PSBGEN or ACBGEN when APPLCTN PSB= is specified. When APPLCTN GPSB= is specified, a PSBGEN or ACBGEN is not required.

CPI-C driven application programs must begin with the CPI-C verbs, ACCEPT and RECEIVE, to initiate the LU 6.2 conversation. You can then issue the APSB call to allocate a PSB for use by the application program. After the APSB call is issued, you can issue additional DL/I calls using the PCBs that were allocated. You then issue the SRRCMIT verb to commit changes or the SRRBACK verb to back out changes. To use SRRCMIT and SRRBACK, your application program must be linked with DFSCPIR0.

To deallocate the PSB in use, issue the DPSB call. You can then issue another APSB call, or use the CPI-C verb, DEALLOCATE, to end the conversation.

CPI-C driven application programs are considered discardable (unless they are allocated with a SYNCLVL=SYNCPT) by IMS TM and are therefore not recovered automatically at system failure. If they are allocated with a SYNCLVL=SYNCPT, a two-phase commit process is used to recover from any failures. The general format of a CPI-C driven application program is shown in the following code example.