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[netCDF #ZNH-695875]: ncopen function

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  • Subject: [netCDF #ZNH-695875]: ncopen function
  • Date: Thu, 24 Sep 2009 10:41:48 -0600
Hi Thomas,

> I have created a netCDF file containing climatologic data that is 2.3G big.
> Unfortunately when I try to open it with a program called "XConv" I get an
> error message saying:
> 
> ncopen: filename "/Output/snow/driving_data.nc": Value too large for defined
> data type
> 
> Could you please tell me what is the maximum size of a file that the ncopen
> function can handle? Or should I contact the creators of "XConv" for this?

You may have to contact the XConv developers to find out what version
of the netCDF library XConv is linked with.  Issues with earlier
versions of netCDF files and file sizes are summarized in these
frequently asked questions about netCDF and Large File Support:

  http://www.unidata.ucar.edu/netcdf/docs/faq.html#Large%20File%20Support

A summary answer is that any recent version of the netCDF library
(version 3.6.1 or later) should be able to access very large files
with the nc_open function.  Typically problems with large files occur
when trying to write the file with netCDF, not when trying to read it
(or open it).

The error message "Value too large for defined data type" is not one
emitted by nc_open.  It appears to be a file system error that
indicates that your file system is not configured for large files.  On
a Unix system, you can test this with a commands such as

  dd if=/dev/zero bs=1000000 count=3000 of=./largefile
  ls -l largefile
  rm largefile

which should write a 3 GByte file named "largefile" in the current
directory, verify its size, and remove it.

A simple test for whether your installed netCDF library can handle the
file would be to use the "ncdump" utility, which also calls nc_open to
open the file.  For example, to see just the header information in the
file, invoke:

  ncdump -h /Output/snow/driving_data.nc

and if you get the expected output rather than an error message, then
nc_open in the installed library that ncdump is linked to is working
OK.  To see what version of the library ncdump was compiled with, try

  ncdump -version

and look at the last line of the output, which unless your netCDF
installation is very old should be something like

  netcdf library version 4.1-beta2 of Sep 14 2009 15:51:36 $

--Russ

Russ Rew                                         UCAR Unidata Program
address@hidden                     http://www.unidata.ucar.edu



Ticket Details
===================
Ticket ID: ZNH-695875
Department: Support netCDF
Priority: Normal
Status: Closed