Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Thu, 5 Jun 2014 16:09:56 -0500

On 06/05/2014 03:56 PM, Eric Norum wrote:
> I’m not sure that this is a good idea.  Having different clients
> behave differently seems like it’s going to cause a lot more problems
> than it solves.

I agree; the best solution for most modern clients should be to set
EPICS_CA_MAX_ARRAY_BYTES to a very large number in a script that gets
installed into /etc/profile.d so everybody gets that setting without
having to think about it. About the only place where you would want to
avoid doing that would be in embedded IOCs that don't have virtual memory.

You could also put that big number in the configure/CONFIG_SITE_ENV file
of the copy of Base you use for client applications, as long as you use
a different version of Base without that setting for building your
embedded IOCs.

If someone wants to work out how to configure architecture-specific
default settings during the build of Base that might be an interesting
patch for future releases.

- Andrew

> On Jun 5, 2014, at 11:40 AM, Hu, Yong <[email protected]> wrote:
> 
>> Hello All,
>> 
>> I guess many EPICS users, especially beginners, had problems when
>> using the command "caget" to read large waveform data because they
>> forgot to reconfigure EPICS_CA_MAX_ARRAY_BYTES to a bigger number
>> or they didn't know how to configure this parameter. Now, this
>> problem seems to be fixed. See attached patch or .c file. I tested
>> it on Debian 6 / gcc 4.4.5 / base-3.14.12.2.
>> 
>> I hope no users would use the command "camonitor" for big waveform
>> data. Auto-configuring of EPICS_CA_MAX_ARRAY_BYTES in camonitor
>> seems more complicated.
>> 
>> Two years ago, there were discussions about automatically resizing
>> max_array_bytes:
>> http://www.aps.anl.gov/epics/tech-talk/2012/msg02136.php . I have
>> an idea about how to implement this on the ioc side (RSRV), but no
>> progress has been made yet. We just successfully completed NSLS-II
>> Storage Ring phase-I commissioning and our machine is in
>> maintenance. So, I have some free time to work on this again.
>> 
>> All are welcomed to test the attached caget on Windows, Mac, and
>> other Linux distros. Any idea & suggestion is welcomed!
>> 
>> Yong<caget.c-3.14.12.2.patch><caget.c>
> 

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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System