Re: rsrv and cas

[Andrew Johnson <anj@aps.anl.gov>]

Hi Jack,

On 2013-01-07 Jack Smith wrote:
> As Ralph said below, rsrv is the old C Channel Access server. I
> suppose cas is the new C++ Channel Access server. Here are my
> questions:
> 
> 1. Why do we need both rsrv and cas? What functionalities are provided
> in each module?

RSRV is still used by the IOC database.  The APIs to the two servers are 
different.  RSRV is written in C and knows how to talk to the database, CAS is 
written in C++ and has a more general interface, but its data interface turned 
out to *not* be appropriate to use in the IOC, which is why it has never 
replaced RSRV in that role.  There has been a 10+ year long project to write a 
better data interface and modify CAS to make use of it, but it's looking like 
it may be hard to merge that at this point.

> 2. When I use makeBaseApp to create an example IOC application, there
> is one line "example_LIBS += $(EPICS_BASE_IOC_LIBS)" in the app's
> src/Makefile and there is an output message "-lrecIoc -lsoftDevIoc
> -lmiscIoc -lrsrvIoc -ldbtoolsIoc -lasIoc -ldbIoc -lregistryIoc
> -ldbStaticIoc -lca -lCom"  during the app building. I see "rsrvIoc"
> and "ca" are included in the IOC. I suppose the "ca" is the Channel
> Access Client library because an IOC could be Channel Access Server as
> well as Channel Access Client. But I don't see something like 'cas' in
> the linked EPICS base libraries. Where is 'cas' included, dbIoc or
> dbStaticIoc or some else?

CAS is not used by IOCs.  If you use makeBaseApp to create an application with 
type caServer you'll get a sample server application which shows you the 
interface to CAS.  CAS is used by the PV Gateway, the CA Nameserver, and 
various other server interfaces to other control systems.

HTH,

- Andrew
-- 
There is no such thing as a free lunch.  When invited for lunch,
it is best to check if you are there to eat, or to be eaten.
-- Clive Robinson