Experimental Physics and Industrial Control System
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Hello
In my EPICS system, I got similor situation.
Data is only one Ai (or CALC) record. And there is two PC linux EPICS IOCs.
Data is generate on first EPICS IOS and access from second EPICS IOC
(AI record) to read it (CAget).
Both EPICS IOC works each SCAN period 40msec (25Hz).
Channel Archiver is working on the second PC and archiveing both first
and second IOCs data.
Archived data from first IOC is almost perfect, but data from second IOC
have some data loss or like that.
I think this data loss due to same reason of Andrei's trouble.
It means, due to the difference of clock frequency of PC (not CPU
frequency).
For example, first PC may be work at 1.0001 second par 1 second.
And second PC may work at 1.0002 second par 1 second.
In this case, after 400 second, CA cycle of second PC outrun the first
PCs, and double the archived data.
I think this is the source of the problem.
caution: SCAN period on my EPICS IOCs are set at 0.039 second and works
at "almost" 40 msec with 1000Hz tick frequency.
Motoki Ooi
Liyu, Andrei wrote:
Hi,
SNS BLM system has 2 levels. First level is VME based/vxWorks
(IOC). Second level is PC/Windows (PC) - similar CAGateway. IOC sends
data one time per second to PC. Data is arrays (one array (720 floats)
per detector; up to 32 detectors per IOC). Array has information about
serial number of current package. PC checks serial number and prints on
terminal port if data was lost or come twice. Time to time (very seldom)
I read both problems.
SNS works on 1 Hz now. IOC CPU loading ~ 3-5% and PC CPU loading
5%. On 60 Hz IOC will have 30% on 60 Hz. PC doesn't depend of
accelerator rate but depends from clients quantity.
I hoped to use CAArchive to find source of problem. But I met
another problem. Archive lost connection to IOC when IOC/PC connection
was Ok.
Does anyone see this problem? Any other suggestions to find the
source (IOC, network, PC)?
Thanks, Andrei.
- References:
- CA loss package on 1 Hz rate Liyu, Andrei
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ANJ, 02 Sep 2010 |
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