RE: MCH3601 errors

David Gibbs wrote:

>I've got a particularly perplexing problem with a MCH3601 exception.
>
>I understand that this error is often caused by a missing, or incorrectly
>specified, parameter on a program call.  Unfortunately, I can't figure out
>where the parameter error is.  I've looked at everything near the failure
>point, both RPG and CL, and everything jives with the docs.

David, the coding error could have happened long before the MCH3601, maybe
even in an earlier program.  What operation are you doing when the MCH
occurs?
Try copying the exact operation to earlier in your code.  If it works ok,
move
it later until you track down where the problem start from.  (It's not
always
possible to move operations around, but often it is, even if you have to
hardcode key values etc.)

Another technique we've used is to add huge amounts of padding to the ends
of
variables used as parameters.  If that makes the problem go away, all you
have
to do is set the padding areas to some value like all 'z' or something, and
when the failure occurs, see which padding area has been changed.  Then
track
down where that variable is changed, using the debugger watch command.

A common source of MCH3601 is misusing the receive-data-queue API, thinking
that the third(?) length parameter is for you to say how long your receiver
is.  Actually, it's for the API to pass back how much it gave you, so you
have to declare the receiver at least as long as the maximum queue entry.

Barbara Morris

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