Experimental Physics and
Industrial Control System

Jeff Hill <[email protected]> · Thu, 14 Nov 1996 10:24:25 -0700

Pete Jemian wrote:
> 
> Is there a field of a process variable that identifies what
> type of record (maybe RTYP) the variable is?
> 

sorry, no.

> How can a Channel Access client find out what type
> of record (ai, ao, steppermotor, etc.) a particular
> process variable is?

When we designed EPICS we intentionally isolated the 
CA clients from any changes which might occur at the record 
level. We wanted to avoid a situation where source code 
changes at the record level resulted in parallel source
code changes in the general purpose clients such as dm, 
medm, alh, etc. This approach has resulted in lower 
maintenance costs for the client side tools.

While we feel that in general it is undesirable for high
level general purpose tools to know what record they are 
attached to, we also see that in many application specific
situations it would be quite useful to have access to this 
information. Perhaps we should add a new "record
type name" data type to the database access level  (which
I assume could only be fetched as a string). Client
requests fetching this type against an old CA server 
that does not support it would be refused.

Is there general interest in this change?

Jeff

-- 
______________________________________________________________________
Jeffrey O. Hill                 Internet        [email protected]
LANL MS H820                    Voice           505 665 1831
Los Alamos, NM 87545 USA        FAX             505 665 5107

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System