[gradsusr] Problem: extracting a variable from a big file

[Matias Mendez]

Dear GrADS users,

I have a big MM5 output (~100GB, with 31 sigma-levels, 742 hourly time
steps, 23 variables). I have used mm5_to_grads.sh to extract a
variable (u-wind). After that I tried to display this variable,
everything  was working fine but when I did:

d u(t=623)

I got the following error mesage:

Notice:  Automatic Grid Interpolation Taking Place
Low Level I/O Error:  Seek error on data file
  Data file name = /home/XXXXX/U_ENE-2006.dat
523 rc=-1 fpos=-2145136144 pfi->fhdr=-1
  Error occurred when seeking to byte 9390016
Data Request Error:  Error for variable 'u'
  Error ocurred at column 1
DISPLAY error:  Invalid expression
  Expression = u(t=623)

What does this mean this message and how can I solve this problem?.
Is there another way to extract a variable from a big file?. Any
sugesstion is welcome. Thanks in advance.

Best regards,
Matías

P.S.
This is the ctl file created by mm5_to_grads.sh

dset /home/XXXXX/U_ENE-2006.dat
byteswapped
title MM5 data
undef -9999.
pdef  399  279 lcc   24.00 -102.00  200.00  140.00   30.00   60.00 -102.00   900
0.   9000.
xdef  972 linear -121.69  0.0405
ydef  571 linear   12.15  0.0405
zdef  31 levels
 0.99950
 0.99800
 0.99600
 0.99400
 0.99200
 0.98950
 0.98700
 0.98500
 0.98300
 0.98100
 0.97500
 0.96000
 0.94000
 0.92000
 0.90500
 0.89000
 0.87000
 0.85000
 0.83000
 0.81000
 0.79000
 0.76000
 0.72000
 0.68000
 0.64000
 0.61000
 0.55000
 0.45000
 0.35000
 0.20000
 0.05000
tdef 742 linear 00:00Z01JAN2006   60MN
vars  1
u         31 99 u wind (m/s)
endvars