Re: Channel Archiving

[Roland Mueller <mueller@mail.bessy.de>]

> I looked into the channel archiver as well and came to the conclusion
> that the SDDS toolset developed here at the APS by Mike Borland and
> company is a far supperior solution.

At BESSY an ever increasing number of channels has to be continuously
monitored and archived. Presently our data collection engine is based on
SDDS(*)monitor. The data repository consists of simple directory trees
structured according to date and device context. The data retrieval is done 
with tcl/Tk wrappers around a dozen of SDDS tools. 

On one aspect I do agree: Set up with `minimal' effort (at least for us,
thanks to the APS people) this type of SDDS based archiving structure
provides impressive versatile and reliable capabilities to correlate
various types of events.

Reasons for us to investigate alternatives like the channel archiver are:

- Adaptive data taking (e.g. fixed frequency during bursts, monitor events
during `quiet' times): As far as I know SDDS(*)monitor is based on ezca
doing `get' whereas the channel archiver already adapts the data aquisition 
method to the rate of changes.

- Relational data base as long term archive: This consideration is fed by
the hope that it might be possible to exploit the power of DB query
functionalities for more flexible, integrated and networked
retrieval applications.

> Sddslogger, for instance, can be set up to log PVs at a particular data
> rate for a specified time, etc...  

I could not find documentation/code for this tool yet. What did I miss?

-- 
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Roland M"uller                                             _`\ <,_
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