Using ATI to allocate a session

Front-end transactions are often initiated from terminals. But it is also possible to use the EXEC CICS START command to initiate a front-end transaction on an APPC session.

When this is done, and the front-end transaction is successfully started, a conversation can continue as if an ALLOCATE command had been issued. The only difference is that, when ATI is used, the APPC session is the front-end transaction's principal facility.

Figure 1. Starting an APPC mapped conversation at sync level 2

 * ...
DATA DIVISION.
WORKING-STORAGE SECTION.
* ...
01 FILLER.
02 WS-CONVID PIC X(4).
02 WS-RESP PIC S9(8) COMP.
02 WS-STATE PIC S9(8) COMP.
02 WS-SYSID PIC X(4) VALUE 'SYSB'.
02 WS-PROC PIC X(4) VALUE 'BBBB'.
02 WS-LEN-PROCN PIC S9(4) COMP VALUE +4.
02 WS-SYNC-LVL PIC S9(4) COMP VALUE +2.
* ...
PROCEDURE DIVISION.
* ...
EXEC CICS ALLOCATE SYSID(WS-SYSID) RESP(WS-RESP)
END-EXEC.
IF WS-RESP = DFHRESP(NORMAL)
THEN MOVE EIBRSRCE TO WS-CONVID
ELSE
* ... No session allocated. Examine RESP code.
END-IF.
* ...
EXEC CICS CONNECT PROCESS CONVID(WS-CONVID)
STATE(WS-STATE) RESP(WS-RESP)
PROCNAME(WS-PROC)
PROCLENGTH(WS-LEN-PROCN)
SYNCLEVEL(WS-SYNC-LVL)
END-EXEC.
IF WS-RESP = DFHRESP(NORMAL)
THEN
* ... No errors. Check EIB flags.
ELSE
* ... Conversation not started. Examine RESP code.
END-IF.