[gradsusr] question about "Low Level I/O Error: Seek error on data file"

[Jennifer M Adams]

Hi, Paul —
GrADS is having trouble figuring out where to set the pointer in the data file to read the desired grid — that variable fpos should not be -2110654536. I would try the following strategy:
1. create a separate non-templated descriptor file for this particular data file
2. try to display zvort for the first and last time steps and see if you are still getting the error
3. the fpos variable is calculated based on the current dimension environment and the structure of the data file (order of variables, etc.) so if you can duplicate the error with the one file, please also send the output from ‘q file' and ‘q dims’ before you try your display.
—Jennifer

On Apr 13, 2017, at 9:48 AM, Paul Markowski <pmarkowski at psu.edu<mailto:pmarkowski at psu.edu>> wrote:

Hello Grads users,

I was wondering if anyone has ever seen this Grads error before:

ga-> d zvort
Low Level I/O Error:  Seek error on data file
  Data file name = cm1out_00%y4_s.dat
650 rc=-1 fpos=-2110654536 pfi->fhdr=0
  Error occurred when seeking to byte -8442618144
Data Request Error:  Error for variable 'zvort'
  Error ocurred at column 1
DISPLAY error:  Invalid expression
  Expression = zvort

In case it matters, I'm trying to display output from George Bryan's CM1
model (CM1 is a popular cloud-resolving model used heavily in the
convective storms community, but is also used by the boundary layer and
mountain meteorology communities).  I've used Grads to display CM1
output for 15 years, and this is the first time I've ever seen this
strange error.  It might be noteworthy that I get this error only for
some of the variables that I'm trying to display.  My output file is ~7
GB.  I've tried both Grads 2.0.1 and 2.1.a3; same error with both.  I
don't know if it has to do with the large file size; perhaps there's a
"large memory" compile option that wasn't properly used when the code
was compiled?  I'd be grateful for any insight you might have!

Paul




--
Paul Markowski
Professor of Meteorology
Department of Meteorology and Atmospheric Science
Pennsylvania State University
520 Walker Building
University Park, PA 16802
email: pmarkowski at psu.edu<mailto:pmarkowski at psu.edu>
phone: 814.865.9736
web: http://sites.psu.edu/pmarkowski

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--
Jennifer Miletta Adams
Center for Ocean-Land-Atmosphere Studies (COLA)
George Mason University



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