The following steps describe how to write a COBOL reliable RPC client
program with the scenario Using the COBOL Wrapper for CICS with DFHCOMMAREA
Calling Convention (z/OS and z/VSE) and
Linkage access to RPC communication.
Reliable RPC requires an explicit broker logon. See Using Broker Logon and Logoff.
For every program definition in the Software AG IDL file, the templates will generate a copybook file that describes the customer data of the interface as a COBOL structure. For ease of use, the copybook can be embedded into the RPC client program.
However, if more appropriate, customer data structures can be used. In this case the COBOL data types and structures must match the interfaces of the generated client interface objects, otherwise unpredictable results will occur.
* Declare the customer data of the generated RPC interface 01 SENDMAIL. 02 SM-COMA. 03 SM-TOADDRESS PIC X(60). 03 SM-SUBJECT PIC X(20). 03 SM-TEXT PIC X(100).
The RPC communication area must be declared and initialized in your RPC client program as follows:
* Declare RPC communication area 02 ERX-COMMUNICATION-AREA. COPY ERXCOMM. . . . . . . * Initialize RPC communication area INITIALIZE ERX-COMMUNICATION-AREA. MOVE "2000" to COMM-VERSION.
The following settings to the RPC communication area are required as a minimum to use the COBOL Wrapper. These settings have to be applied in your RPC client program. It is not possible to generate any defaults into your client interface objects:
* assign the broker to talk with MOVE "localhost:1971" to COMM-ETB-BROKER-ID. * assign the server to talk with MOVE "RPC" to COMM-ETB-SERVER-CLASS. MOVE "SRV1" to COMM-ETB-SERVER-NAME. MOVE "CALLNAT" to COMM-ETB-SERVICE-NAME. * assign the user ID for Broker logon MOVE "ERXUSER" to COMM-USERID. MOVE "PASSWORD" to COMM-PASSWORD.
MOVE "LO" TO COMM-FUNCTION. EXEC CICS LINK PROGRAM ("COBSRVI") COMMAREA (ERX-COMMUNICATION-AREA) LENGTH (LENGTH OF ERX-COMMUNICATION-AREA) RESP (CICS-RESP1) RESP2 (CICS-RESP2) END-EXEC.
Check whether the logon call was successful or not.
Before reliable RPC can be used, the reliable state must be set to
either ERX_RELIABLE_CLIENT_COMMIT
or ERX_RELIABLE_AUTO_COMMIT
.
"C" - CLIENT_COMMIT
"A" - AUTO_COMMIT
* Set the reliable RPC mode MOVE "C" TO COMM-RELIABLE-STATE.
The RPC message is sent using the EXEC CICS LINK
interface.
* Send the RPC message MOVE DFHRESP(NORMAL) TO CICS-RESP1. MOVE DFHRESP(NORMAL) TO CICS-RESP2. MOVE ZEROES TO COMM-RETURN-CODE. EXEC CICS LINK PROGRAM ("SENDMAIL") RESP (CICS-RESP1) RESP2 (CICS-RESP2) COMMAREA (SENDMAIL) LENGTH (LENGTH OF SENDMAIL) END-EXEC.
When the RPC message is returned, it needs to be checked whether it was successful or not:
IF COMM-RETURN-CODE IS = ZERO Perform success-handling ELSE Perform error-handling END-IF.
The field COMM-RETURN-CODE
in the RPC communication area contains the
error provided by the COBOL Wrapper.
For the error messages returned, see Error Messages and Codes.
Note:
After successful call (Step 6a) the UOWID
is available in the RPC
communication area field COMM-ETB-UOW-ID
. See The RPC Communication Area (Reference).
To determine that reliable RPC messages are delivered, the reliable RPC message status can be queried. See Understanding UOW Status and Broker UOW Status Transition for more information.
MOVE DFHRESP(NORMAL) TO CICS-RESP1. MOVE DFHRESP(NORMAL) TO CICS-RESP2. MOVE "RS" TO COMM-FUNCTION. MOVE ZEROES TO COMM-RETURN-CODE. EXEC CICS LINK PROGRAM ("COBSRVI") RESP (CICS-RESP1) RESP2 (CICS-RESP2) COMMAREA (ERX-COMMUNICATION-AREA) LENGTH (LENGTH OF ERX-COMMUNICATION-AREA) END-EXEC.
Note:
After successful call the UOW status is available in the RPC
communication area field COMM-RELIABLE-STATUS
. See The RPC Communication Area (Reference).
Check whether the check status call was successful or not.
Send a second reliable RPC message. See Step 6a and Step 6b.
Check the reliable RPC message before the commit call. See Step 7a and Step 7b.
Now both reliable RPC messages are committed. This will deliver all reliable RPC messages to the server if it is available.
MOVE DFHRESP(NORMAL) TO CICS-RESP1. MOVE DFHRESP(NORMAL) TO CICS-RESP2. MOVE "RC" TO COMM-FUNCTION. MOVE ZEROES TO COMM-RETURN-CODE. EXEC CICS LINK PROGRAM ("COBSRVI") RESP (CICS-RESP1) RESP2 (CICS-RESP2) COMMAREA (ERX-COMMUNICATION-AREA) LENGTH (LENGTH OF ERX-COMMUNICATION-AREA) END-EXEC.
Check whether the commit call was successful or not.
Send a third reliable RPC message. See Step 5a and Step 5b.
Check the reliable RPC message before the rollback call. See Step 6.
Roll back the current reliable RPC message.
MOVE DFHRESP(NORMAL) TO CICS-RESP1. MOVE DFHRESP(NORMAL) TO CICS-RESP2. MOVE "RR" TO COMM-FUNCTION. MOVE ZEROES TO COMM-RETURN-CODE. EXEC CICS LINK PROGRAM ("COBSRVI") RESP (CICS-RESP1) RESP2 (CICS-RESP2) COMMAREA (ERX-COMMUNICATION-AREA) LENGTH (LENGTH OF ERX-COMMUNICATION-AREA) END-EXEC.
When the rollback call is returned, check whether it was successful or not. If the rollback call failed, an explicit EOC needs to be sent:
MOVE DFHRESP(NORMAL) TO CICS-RESP1. MOVE DFHRESP(NORMAL) TO CICS-RESP2. MOVE "RS" TO COMM-FUNCTION. MOVE ZEROES TO COMM-RETURN-CODE. EXEC CICS LINK PROGRAM ("COBSRVI") RESP (CICS-RESP1) RESP2 (CICS-RESP2) COMMAREA (ERX-COMMUNICATION-AREA) LENGTH (LENGTH OF ERX-COMMUNICATION-AREA) END-EXEC.
MOVE "LF" TO COMM-FUNCTION. EXEC CICS LINK PROGRAM ("COBSRVI") COMMAREA (ERX-COMMUNICATION-AREA) LENGTH (LENGTH OF ERX-COMMUNICATION-AREA) RESP (CICS-RESP1) RESP2 (CICS-RESP2) END-EXEC.
Check whether the logoff call was successful or not.
There are no server-side methods for reliable RPC. The server does not send back a message to the client. The server can run deferred, thus client and server do not necessarily run at the same time. If the server fails, it returns an error code greater than zero. This causes the transaction (unit of work inside the Broker) to be cancelled, and the error code is written to the user status field of the unit of work. For writing reliable RPC servers, see Using the COBOL Wrapper for the Server Side.
To execute a reliable RPC service with an RPC server, the parameter logon
(LOGN
under CICS) must be set to YES
.
See logon
under
z/OS (CICS |
Batch |
IMS) |
MicroFocus |
BS2000 |
z/VSE (CICS |
Batch).