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Message ID: 13734     Entry time: Fri Apr 6 16:07:18 2018
Author: gautam 
Type: Update 
Category: CDS 
Subject: Frequent EPICS dropouts 

Kira informed me that she was having trouble accessing past data for her PID tuning tests. Looking at the last day of data, it looks like there are frequent EPICS data dropouts, each up to a few hours. Observations (see Attachment #1 for evidence):

  1. Problem seems to be with writing these EPICS channels to frames, as the StripTool traces do not show the same discontinuities.
  2. Problem does not seem local to c1auxex (new Acromag machine). These dropouts are also happening in other EPICS channel records. I have plotted PMC REFL, which is logged by the slow machine c1psl, and you can see the dropouts happen at the same times.
  3. Problem does not seem to happen to the fast channel DQ records (see ETMX Sensor record plotted for 24 hours, there are no discontinuties).

It is difficult to diagnose how long this has been going on for, as once you start pulling longer stretches of data on dataviewer, any "data freezes" are washed out in the extent of data plotted.

Attachment 1: EPICS_dropout.png  38 kB  Uploaded Fri Apr 6 17:12:16 2018  | Hide | Hide all
EPICS_dropout.png
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