Example: Wait up to two hours to receive data from data queue

In the following example, program B specifies to wait up to two hours (7200 seconds) to receive an entry from the data queue. Program A sends an entry to data queue DTAQ1 in library QGPL. If program A sends an entry within two hours, program B receives the entries from this data queue. Processing begins immediately. If two hours elapse without procedure A sending an entry, program B processes the time-out condition because the field length returned is 0. Program B continues receiving entries until this time-out condition occurs. The programs are written in CL; however, either program could be written in any high-level language.

The data queue is created with the following command:

CRTDTAQ DTAQ(QGPL/DTAQ1) MAXLEN(80)

In this example, all data queue entries are 80 bytes long.

In program A, the following statements relate to the data queue:

PGM
DCL  &FLDLEN  *DEC  LEN(5 0)  VALUE(80)
DCL  &FIELD  *CHAR  LEN(80)
.
.(determine data to be sent to the queue)
.
CALL  QSNDDTAQ  PARM(DTAQ1 QGPL &FLDLEN &FIELD)
.
.
.

In program B, the following statements relate to the data queue:

        PGM
        DCL  &FLDLEN  *DEC  LEN(5 0)  VALUE(80)
        DCL  &FIELD  *CHAR  LEN(80)
        DCL  &WAIT  *DEC  LEN(5 0)  VALUE(7200)   /* 2 hours */
        .
        .
        .
LOOP:   CALL QRCVDTAQ  PARM(DTAQ1 QGPL &FLDLEN &FIELD &WAIT)
        IF    (&FLDLEN *NE 0) DO   /* Entry received */
               .
               . (process data from data queue)
               .
               GOTO LOOP   /* Get next entry from data queue */
        ENDDO
        .
        . (no entries received for 2 hours; process time-out condition)
        .