This document of the Natural CICS Interface documentation explains special Natural CICS functionality.
It covers the following sections:
One of the first actions a Natural task does at its start, is to
activate an exit for abnormal termination processing. This exit is used to
release all resources including the thread in the case of an abnormal
termination. Therefore, a non-Natural program must not issue EXEC
CICS ABEND CANCEL or the equivalent macro level request, as such
a request cancels the current session ignoring any active exit. If so, Natural
is not able to clean up its resources, and the thread and the roll facility are
not released.
A thread is assigned to a Natural task whenever a Natural program is active. This is also true when non-Natural programs are called (following CICS linkage conventions).
Therefore, such programs should not do excessive I/Os and other work
load without Natural receiving control in between. If a non-Natural program is
doing conversational screen I/Os, you can code a SET CONTROL 'P=V'
statement in the Natural program that calls the non-Natural program before the
calling statement: this indicates that parameter data are copied out of the
thread and the session is rolled out before calling the non-Natural
program.
A non-Natural program is invoked (CALLed) by Natural in the way programs are invoked within the underlying operating and/or TP monitor system.
In CICS, non-Natural programs are invoked by means of EXEC
CICS LINK requests. However, when, for example, the same
subroutine program (not issuing any CICS or operating system request) is to be
used for both batch and online processing, a non-Natural program may also be
invoked by using CICS standard linkage conventions; that is, via BALR
R14,R15.
For further information, see the terminal command
%P=S in the
Terminal Commands
documentation. See also the parameter
SLCALL in
macro NTCICSP.
By default, non-Natural programs are called with the addresses of the
request parameter lists (see the description of the
CALL statement in the
Natural Statements documentation) passed in the TWA and/or
a COMMAREA (depending on the setting of the NTCICSP parameter
CALLRPL).
A more CICS-like method is to pass the parameter values in a CICS COMMAREA or a CICS Container (see Natural CICS Interface Support for CICS Channels and Containers), particularly when the called program resides in another CICS region - Distributed Program Link (DPL) -, as addresses within the "calling" region are not accessible by the "called" region.
For details and restrictions, see the terminal commands
%P=C and
%P=CC in the
Terminal Commands documentation.
This functionality requires CALLRPL to be set to
ON in NTCICSP.
When the parameter values are passed in a CICS COMMAREA or CICS
container, no parameter list pointers are passed in the CICS TWA, regardless of
the CALLRPL setting.
If a SET CONTROL 'QO' statement is placed before a Natural
statement that causes a screen I/O, the terminal output is not executed by
Natural under CICS. Consequently, both the Enter key and user input
are not passed back to Natural.
This functionality may be useful in the following situations:
When leaving pseudo-conversational screen I/Os to non-Natural programs
called by Natural. The non-Natural program performs the EXEC CICS
SEND operation and returns to Natural. Due to the SET
CONTROL 'QO' statement, the next Natural screen I/O terminates the task
of a pseudo-conversational session. Upon screen input, Natural receives control
and invokes the non-Natural program again, which then performs the
EXEC CICS RECEIVE.
When changing the Natural pseudo-conversational transaction ID "in-flight" without requiring a terminal operator intervention:
MOVE *INIT-ID TO termid CALLNAT 'CMTRNSET' trnid /* change the restart transaction ID * starting a task on your terminal forces an interrupt as if * pressing any attention identifier CALL 'CMTASK' USING trnid H'0000' H'00000000' termid SET CONTROL 'QO' INPUT 'DUMMY' /* dummy I/O, which you will never see WRITE 'HELLO' *INIT-PROGRAM /* now the new transaction ID is active
When switching to an application outside Natural, perhaps even in another CICS AOR (application-owning region), without requiring a terminal operator intervention:
* starting a task on your terminal forces an interrupt as if * pressing any attention identifier CALL 'CMTASK' USING trnid data-length start-data termid SET CONTROL 'QO' INPUT 'DUMMY' /* dummy I/O, which you will never see WRITE 'HELLO' *INIT-PROGRAM /* now the new transaction ID is active
In this case, it is the responsibility of the application being invoked to stack the Natural restart data when they are passed in a CICS COMMAREA, as a COMMAREA most likely is used by the new (pseudo-conversational) application, too.