RE: QRCVDTAQ (Receive Data Queue) program

[qsrvbas@xxxxxxxxxxxx (Tom Liotta)]

rpg400-l-request@xxxxxxxxxxxx wrote:

>   6. Re: QRCVDTAQ (Receive Data Queue) program (Nathan Hiley)
>
>My code is as follows:
>
>DCL VAR(&QNAMEO)  TYPE(*CHAR) LEN(10)
>DCL VAR(&KEY)     TYPE(*CHAR) LEN(87) (key passed in)
>DCL VAR(&WAITQ)   TYPE(*DEC)  LEN(5 0) (passed in - set to 7 seconds)
>DCL VAR(&RPYDTA)  TYPE(*CHAR) LEN(2378) VALUE(' ')
>DCL VAR(&SENDER)  TYPE(*CHAR) LEN(10)  VALUE(' ')
>DCL VAR(&SNDLEN)  TYPE(*DEC)  LEN(3 0) VALUE(0)  
>DCL VAR(&RPYLEN)  TYPE(*DEC)  LEN(5 0) VALUE(0)
>DCL VAR(&RPYLEC)  TYPE(*CHAR) LEN(5) VALUE(' ')
>:
>:
>CALL PGM(QRCVDTAQ) PARM(&QNAMEO '*LIBL     ' &RPYLEN &RPYDTA &WAITQ 'EQ' +
>                        &KEYLEN &KEY &SNDLEN &SENDER)
>CHGVAR VAR(&RPYLEC) VALUE(&RPYLEN) (MCH3601 on this line)
>
>The data queue in &QNAMEO is a standard, keyed queue, key length=87, 
>include_sender_id=*no, max_length=11721.
>
>Can anyone see a problem with the above? If not, what else could be the cause 
>of the problem. Any help would be greatly appreciated.

Nathan:

I haven't looked in detail, but was immediately caught by three elements. First 
is this source line:

>DCL VAR(&RPYDTA)  TYPE(*CHAR) LEN(2378) VALUE(' ')

Second is this statement of yours:

>The data queue in &QNAMEO is a standard, keyed queue, key length=87, 
>include_sender_id=*no, max_length=11721.

And third is the absense of optional parameter group 2 for the API. That 
parameter group includes the Size of data receiver parm. Without telling the 
API how big your receiver variable (&RPYDTA) is, there's no telling what memory 
might get blasted when the API returns a message that's longer than 2378.

Just the kind of thing that could contribute to MCH3601 errors, AFAIK.

In fact, since the maximum size of a data queue message from that data queue is 
longer than the largest possible CL variable, you probably should expect a 
problem sooner or later regardless of what messages are currently on the queue 
(unless you limit what the API returns).

Tom Liotta