Experimental Physics and
Industrial Control System

Tim Mooney <[email protected]> · Wed, 15 Jul 2009 10:15:05 -0500

Andrew Johnson wrote:

On Tuesday 14 July 2009 17:53:25 Benjamin Franksen wrote:

On Dienstag, 14. Juli 2009, Tim Mooney wrote:

Benjamin Franksen wrote:

I get this message on the iocsh (base is 3.14.8.2):

dbCaTask ca_array_put Channel write request failed
OTERMPCGP:cmdRmp has DB CA link to OTERMPCGP:colStRmp.PROC

Ben,  I get that same error message when I use a CA link (from any
record) to
process a  record whose processing results in an error.  If your
situation is
like mine, OTERMPCGP:colStRmp should be in some kind of alarm.

Interesting. I'll check this. The message is a bit misleading (if this is
indeed what causes it), to me it suggests that I have somehow misconfigured
the link.

I agree the message is misleading. It occurs because any error status

returned by device support is passed back up the call chain and is returned

by the record type's process() routine, by dbProcess(), then by dbPutField().

db_put_field converts it to a 0 or -1 value and results in the channel access

server reporting a write error to the client, which in this case is the dbCa

link where your error message came from.

I would be interested in any thoughts on whereabouts in the above chain we

should clear any error status from device support. I suspect it should be

the record type's responsibility once it has put the record into an alarm

state (thus handling and reporting the error), but I could be persuaded

otherwise.

- Andrew

I think it's a great thing to have a message identifying the record whose
CA link caused the processing that failed.  I think a less generic error
message would be an improvement.  People expect an error message to say
what's wrong; the message "<record> has a DB CA link..." gives context for
the previous message, but I read it as implying something wrong with the link.
For me, it would be clearer if the message said something like "An error
occurred while <record A> was writing, via a DB CA link, to <record B>".

--
Tim Mooney ([email protected]) (630)252-5417
Beamline Controls & Data Acquisition Group
Advanced Photon Source, Argonne National Lab.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System