Testing Whether a Transaction Has Started


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Programming a BEA Tuxedo Application Using COBOL

It is important to know whether or not a process is in transaction mode in order to avoid and interpret certain error conditions. For example, it is an error for a process already in transaction mode to call TPBEGIN. When TPBEGIN is called by such a process, it fails and sets TP-STATUS to TPEPROTO to indicate that it was invoked while the caller was already participating in a transaction. The transaction is not affected.

You can design a service subroutine so that it tests whether it is in transaction mode before invoking TPBEGIN. You can test the transaction level by either of the following methods:

Querying the settings of the service information structure that is passed to the service routine. The service is in transaction mode if the value is set to TPTRAN.
Calling the TPGETLEV(3cbl) routine.

Use the following signature to call the TPGETLEV routine.

01 TPTRXLEV-REC.
   COPY TPTRXLEV.
01 TPSTATUS-REC.
   COPY TPSTATUS.
CALL "TPGETLEV" USING TPTRXLEV-REC TPSTATUS-REC.

TPGETLEV returns TP-NOT-IN-TRAN if the caller is not in a transaction and TP-IN-TRAN if the caller is.

The following code sample shows how to test for transaction level using the TPGETLEV routine (line 3). If the process is not already in transaction mode, the application starts a transaction (line 5). If TPBEGIN fails, a message is returned to the status line (line 9) and APPL-CODE IN TPSVCRET-REC of TPRETURN is set to a code that can be retrieved in APL-RETURN-CODE IN TPSTATUS-REC (lines 1 and 11).

Testing Transaction Level

     . . . Application defined codes
001      77 BEG-FAILED    PIC S9(9) VALUE 3.
     . . .
002  PROCEDURE DIVISION.
     . . .
003  CALL "TPGETLEV" USING TPTRCLEV-REC
                     TPSTATUS-REC.
004  IF NOT TPOK
        error processing  EXIT PROGRAM
005  IF TP-NOT-IN-TRAN
006         MOVE 30 TO T-OUT.
007         CALL "TPBEGIN" USING
                           TPTRXDEF-REC
                           TPSTATUS-REC.
008         IF  NOT TPOK
009              MOVE "Attempt to TPBEGIN within service failed"
                           TO USER-MESSAGE.
010              SET TPFAIL TO TRUE.
011              MOVE BEG-FAILED TO APPL-CODE.
012              COPY TPRETURN REPLACING
013                        DATA-REC BY USER-MESSAGE.
     . . .

If the AUTOTRAN parameter is set to Y, you do not need to call the TPBEGIN, and TPCOMMIT or TPABORT transaction routines explicitly. As a result, you can avoid the overhead of testing for transaction level. In addition, you can set the TRANTIME parameter to specify the time-out interval: the amount of time that may elapse after a transaction for a service begins, and before it is rolled back if not completed.

For example, suppose you are revising the OPEN_ACCT service shown in the preceding code listing. Currently, OPEN_ACCT defines the transaction explicitly and then tests for its existence. To reduce the overhead introduced by these tasks, you can eliminate them from the code. Therefore, you need to require that whenever OPEN_ACCT is called, it is called in transaction mode. To specify this requirement, enable the AUTOTRAN and TRANTIME system parameters in the configuration file.