potential cause for "Low Level I/O Error"

Tue Apr 22 20:05:27 EDT 2008

I get the following error when trying to access parts of a binary file:

Low Level I/O Error:  Seek error on data file
  Data file name =
/disk/c2/ofes/Tropical_Pacific/hbudget/post_4601/source.dta
657 rc=-1 pos=536871600 pfi->fhdr =0
Segmentation fault

GrADS then exits upon encountering this problem.  The file contains
a single variable with (x,y,z,t) dimensions of 3600x420x54x31 and I
get the error when trying to access beyond time=7, level=32, y=32.
I wrote a script to read the data file, and there does not appear to be
anything strange (e.g., NaN's).  However, the data are extremely small
(order 10^-19).  Could this be the problem?  Or, is there a meaning to
the error that would help sort this out?  Thanks,

Jim
-------------------------------------------
GrADS running on Redhat EL-4:

Config: v1.9.0-rc1 32-bit little-endian readline sdf/xdf netcdf dap
dap-stn lats athena printim

Grid Analysis and Display System (GrADS) Version 1.9.0-rc1
Copyright (c) 1988-2005 by Brian Doty and IGES
Center for Ocean-Land-Atmosphere Studies (COLA)
Institute for Global Environment and Society (IGES)
This program is distributed WITHOUT ANY WARRANTY
See file COPYRIGHT for more information.

Built Fri Jan 25 17:02:09 EST 2008 for i686-pc-linux-gnu

This version of GrADS has been configured with the following options:

   o This is a 32-bit LITTLE ENDIAN machine version.
   o Command line editing (readline) ENABLED.
   o CIRES/CDC (http://www.cdc.noaa.gov) SDF/XDF interface ENABLED.
     Use sdfopen/xdfopen to read NetCDF files.
   o DTYPE netcdf is ENABLED; DTYPE hdfsds is DISABLED.
   o OPeNDAP (a.k.a. DODS) gridded data interface ENABLED.
(http://opendap.org)
     This version is configured to access gridded data on OPeNDAP servers
     via the sdfopen or xdfopen commands, or using DTYPE netcdf.
   o OPeNDAP (a.k.a. DODS) station data interface (gadap) ENABLED.
     This version is configured to access station data on OPeNDAP servers
     via the open command.
   o PCMDI (http://www-pcmdi.llnl.gov) LATS interface ENABLED.
     This version is configured to write GRIB and NetCDF files.
   o DAO (http://dao.gsfc.nasa.gov) Athena Widget GUI ENABLED.
   o NRL/DAO/PCMDI XA or ImageMagick Image Output DISABLED.
   o printim command for direct png/gif output ENABLED.
     (via the GD Library -- http://www.boutell.com/gd)

For additional information please consult http://grads.iges.org/grads/
----------------------------
ctl file:
DSET ^/disk/c2/ofes/Tropical_Pacific/hbudget/post_4601/source.dta
OPTIONS big_endian
TITLE OFES Heat flux daily snapshots, clim forcing
UNDEF -9.999999999999999E+33
XDEF 3600 linear 0.05 0.1
YDEF 420 linear -20.95 0.1
ZDEF 54 LEVELS
 2.500000 7.561558 12.806275 18.351244
 24.306158 30.770624 37.831699 45.561745
 54.016659 63.234489 73.234489 84.016663
 95.561745 107.831696 120.770622 134.306152
 148.351242 162.806274 177.561554 192.500000
 207.500000 223.171860 240.853607 261.866058
 287.501678 319.013458 357.604279 404.416565
 460.522644 526.915588 604.500610 694.087585
 796.383789 911.988220 1041.386353 1184.945801
 1342.913452 1515.413452 1702.445801 1903.886353
 2119.488281 2348.883789 2591.587646 2847.000732
 3114.415527 3393.022705 3681.916504 3980.104248
 4286.513672 4600.001465 4919.366211 5243.353516
 5570.671875 5900.000000
TDEF  31 LINEAR 01jan0046 1dy
VARS 1
source 54 0 source term
ENDVARS