Experimental Physics and
Industrial Control System

Luedeke Andreas <[email protected]> · Fri, 02 Jul 2004 21:23:51 +0200

Andrew Johnson wrote:
[...]

Bear in mind that the list of PVs (i.e. CA Channel names) is not the
same as the output from dbl, which just gives you the record names. A
truly omniscient nameserver would also need to know the record type,
and the set of publicly accessible field names for that record type on
that particular IOC [don't forget that two IOCs that use two different
DBD files can have a different set of fields in the same record type,
you must make sure you're using the IOC's DBD file to be sure what
fields it will have]. A simple way to resolve this would be to dump
the DBD file at boot time as well as the dbl output.

Of course we put the record type (and description field) to the
database, too. At the moment we just upload the dbd file once to the
database, since we use the same set of records everywhere. But I agree
that it would be more generic and is required for more heterogenious
setups, to put one dbd file per IOC to the database. Actually, that is
very easy to add, just a minor extension to the "ioc_channels" table.
It should be relatively straightforward to write some IOC-side code
which queries the database in memory using dbStaticLib routines, and
sends the results directly to the name server; I'm not aware of anyone
who has actually implemented something like this though. This code
would be able to resolve the field names issue without having to write
a parser to extract the DBD filename(s) from the st.cmd file.

Yes, that's a very good idea! I would volunteer to beta test it as soon
as there's something to test ;-)
Andreas

BTW: the above is just the "repository of provided channels". We have a
second set of scripts to generate a "repository or requested channels".
It parses our application launcher for all used commands to retrieve a
list of channels required from medm panels, Striptools, Alarmhandler,
Archiver and so on. That again should be part of the EPICS applications
to provide command line options to just parse their configuration files
and return a list of channels and secondary program calls. Or better to
write all this to a DB.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System