Re: recordGenerator record

[Ned Arnold <nda@aps.anl.gov>]

"Hot add/delete" has been an often discussed desirable feature for the past 15 years ... I'm not surprised that someone has actually attempted it ... go for it !

However, this approach might be a bother if you have to do an unplanned reboot after someone has added several new record instances ...

Other discussions I've heard hypothesized reloading .db files (without rebooting) so a reboot would always catch the latest ...  maybe add the feature to your record to read the .db file and skip over any records that already exist ???

Just a thought ... 

   Ned


----- Original Message -----
From: Steve Lewis <SALewis@llnl.gov>
Date: Friday, October 24, 2008 9:15 am
Subject: Re: recordGenerator record
To: Kalantari Babak <BABAK.KALANTARI@psi.ch>
Cc: tech-talk@aps.anl.gov

> This is definitely a good idea.  I often wish I had just 
> one more 
> calc record on a running IOC so I could add a derived value 
> (power 
> from voltage and current; take a logarithm; etc).  You can 
> always 
> leave a few around named "temp_1", "temp_2" and so forth, but 
> this 
> seems much more elegant.  Another use is adding a history 
> record.  To 
> avoid any lock-set issues, records like these can always use 
> "CPP" 
> links--which I do anyway in such circumstances since I don't 
> like to 
> clutter the "hard" code with forward links to "soft" code.
> 
> At 3:56 PM +0200 2008/10/24, Kalantari Babak wrote:
> >I have spent some time on writing a new EPICS record type which can
> >create new record instances at IOC runtime. At the moment the 
> code is in
> >very preliminary level but it works. "It works" means I am able to
> >generate instances of almost any record types at IOC runtime. The
> >behavior is as the following:
> >
> >1. User specifies record type e.g. "ao", "calc", etc. by CA/DB-
> write to
> >a field of "recordGenerator" record
> >
> >2. User specifies the channel name by CA/DB-write to a field of
> >"recordGenerator" record
> >
> >- As a result a channel with soft device support (soft channel) with
> >corresponding type and name is generated.
> >
> >The generated records behave like a normal record which is 
> generated at
> >init time from static EPICS database (template files). They can be
> >accessed by clients, linked to other records, etc. I have 
> mainly used
> >facilities provided by "dbStatic" library to do this 
> implementation. I
> >had some difficulties with lock-sets but made a work-around 
> just to get
> >it working, but I believe it can be done in a proper way.
> >
> >One potential usage of this may be to have (soft) waveform 
> records which
> >can have changeable size. One way to do this is to copy the 
> content of
> >the generated waveform record, then delete existing record and 
> generate>another one with the new size and fill it in with the 
> data copied from
> >the previous waveform.
> >
> >The questions to me are:
> >
> >1. are there any interests (now/in future) in such a record 
> type, in
> >another word, is it worth at all to put efforts for such thing?
> >
> >2. (if yes) what features such record type can/must have?
> >
> >Any idea/comment is welcome.