Experimental Physics and
Industrial Control System

"Jeff Hill" <[email protected]> · Thu, 9 Sep 2004 12:02:44 -0600

> 	If client connects to IOC then IOC allocates some resource for
> the client. Client should free resource. If a lot of clients wouldn't
> free that IOC should crash.

The IOC might run low on memory blocks of sufficient size, but it should not
crash.

> 
> 	What will we have with Gateway? 

The GW's purpose is to transform the load of N external clients into an
effective inside IOC load similar to what is imposed by one client. This is
much better for an overloaded IOC, but of course the load is transferred to
the GW. A distributed system is converted to a centralized system. There is
a single point of failure and activity levels can be high in the GW as it is
a central bottleneck between M IOCs and N clients. This effect is mitigated
somewhat by the GW's ability to run on cost effective SMP virtual memory
systems (high performance VME processors with enormous memories tend to be a
bit pricey compared to Linux and windows boxes). You can also spread load
across as many gateways as you have the time and inclination to install.

> Can I debug client and don't think about Gateway and IOC servers?

Almost, but note that depending on configuration the GW will forward all
write requests (and any associated load) to the IOC. Note also that if you
don't want your tests to interfere with a GW essential to your operations
then you could start up a private GW that is only used for testing purposes.

Jeff

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System