Re: CA WAN/gateway extensions notes

[mooney@oxygen.aps1.anl.gov (Tim Mooney)]

mrk@phebos.aps.anl.gov writes:

> APS will ultimately have ~36 beam line sectors. Each sector will have an
> arbitrary number of workstations that can potentially want info from the APS
> accelerator control system. If we merely use gateways and access security then
> each beam line CA client will use resources in one or more of the controls
> IOCs. Since this is an unknown and potentially very large usage of ioc
> resources, especially memory, this could be a major problem.
>
> I can think of an easy out. For each sector there is an IOC for control of the beam
> line insertion device. This beam line IOC is managed by accelerator controls
> not by the beam line users. It seems natural to use this IOC as a concentrator.
> We (accelerator controls) could define records to link to all accelerator PVs
> needed by the users. A user connects to one of these records rather than to
> the actual IOC containing the PV to be monitored/controlled. No matter how
> many users connect to the beam line ioc, the number of channel access
> clients connected to the rest of the control network will not change. The
> worst thing the users could do is cause problems with their beam line ioc.
> With proper design this should only affect them and not the users of other
> beam lines.

To set a scale, let's assume each sector will have 10 workstations on
the experimental floor and 10 more in nearby offices.  I think this is
an overestimate, and certainly many of these workstations will not need
to look at accelerator-control information, although users are likely
to leave unneeded displays of accelerator information running.

Is it generally accepted that the problem mostly concerns IOC resources
and not controls-network bandwidth?  I've been assuming neither
controls IOCs nor the controls network are useable by beamline
scientists, and that the concentrator would be a fast workstation
running (more likely, pretending to run) an EPICS database.

Tim Mooney