Experimental Physics and
Industrial Control System

Benjamin Franksen via Core-talk <[email protected]> · Thu, 22 Nov 2018 16:13:20 +0100

Am 19.11.18 um 18:29 schrieb Johnson, Andrew N. via Core-talk:
> The CA protocol's channel name length is not limited by the size of the
> NAME field in the IOC.

I am aware of that. Sorry for not expressing myself clearly.

> Ben, what limitations are you trying to solve, and how do you know that
> they actually exist?

Basically, the limit of 40 bytes on the DBR_STRING data type. Which in
turn implies a limit on the length of things you can put into link
field. Which in turn /effectively/ forces users to limit the record name
length to ~30 bytes, so that togetehr with dot, field name, and link
options it will not reach 40 bytes.

I guess the limit exists only when you write to the field using CA.
Still means that if you want to allow that, you should restrict record
names to be no longer than the ~30 bytes.

I know it exists, because I have been running into this problem every
now and then over the years. Because sometimes people design databases
without knowing of the size limitations and then it's not possible to
write to a link field that targets that record using CA.

Cheers
Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System