Experimental Physics and
Industrial Control System

"Gurd, Pamela A." <[email protected]> · Fri, 17 Nov 2006 12:33:20 -0500

It's true that we have had problems with the sequencer going over 28
characters, but I think they're less of a problem than it would be to
try to stay within 28 characters.

> -----Original Message-----
> From: Andrew Johnson [mailto:[email protected]]
> Sent: Friday, November 17, 2006 12:28 PM
> Cc: tech talk
> Subject: Re: Naming conventions for devices and Epics records
> 
> I would also suggest that you try *really* hard to limit your record
> names to the maximum recommended 28 characters.  You *can* make them
> longer (up to 60 characters), but until the EPICS 40 character string
> length limit goes away (which means until the Channel Access protocol
> gets revised and the database and all of the tools are modified to use
> variable length strings) using longer names *will* end up causing you
> difficulties.  SNS thought they had got away with using longer names
but
> they found problems with long strings in the SNC/Sequencer, which I
> don't think they've managed to fix.
> 
> Why is the recommended limit only 28 characters?  Well if you want to
> change a link field via Channel Access you only have 40 characters to
> hold the complete link value, and as well as the record name the link
> might need dot field name (5 chars with the standard record types) and
> the flags NPP/PP/CA/CP/CPP and NMS/MS which will need another 7 chars
> (you can omit the space between them if necessary, but not the one
that
> terminates the field name).  That leaves just 28 characters for the
> name, and yes I am allowed to leave the terminating \0 byte out of
that
> calculation.
> 
> - Andrew
> --
> There is considerable overlap between the intelligence of the smartest
> bears and the dumbest tourists -- Yosemite National Park Ranger

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System