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

[Eric Aligo]

Hi Jennifer,
I've encountered the same issue as Paul with two different versions of 
GraDS.  My workaround is to split the file into multiple sub files, but 
that's undesirable.  At some point I will try to duplicate the error and 
send the requested info as well.
Eric
On 04/13/2017 11:00 AM, Jennifer M Adams wrote:
> 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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-- 
Dr. Eric Aligo
I. M. Systems Group, Regional Model Developer
NCEP/EMC
5830 University Research Court
College Park, MD  20740, USA
Phone (301) 683-3686

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