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Re: 20020612: RE: 20020607: netCDF error -31

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  • Subject: Re: 20020612: RE: 20020607: netCDF error -31
  • Date: Thu, 13 Jun 2002 13:37:18 -0600
>To: Unidata Support <address@hidden>
>cc: support-netcdf <address@hidden>
>From: psanhuez <address@hidden>
>Subject: RE: 20020607: netCDF error -31
>Organization: UCAR/Unidata
>Keywords: 200206121857.g5CIvCJ16085

Hi Pedro,

> netcdf.h indicate that error number -31 is a system error (no much 
> explanation), but netcdf.inc says that error ?31 means too many netcdfs open. 
> I have no idea when I have to change the number of netcdf open? (what 
> files/parameters).

NetCDF 2.4.3 and earlier versions had a limit of 32 on the number of
netCDF files you could have open at once , but no version released
since 1996 has any such limit other than what the underlying operating
system allows.  These earlier versions may have used the error code
"-31" to indicate you had exceeded the 32-file limit for open netCDF
files.

In the current versions, the error code -31 does not correspond to any
netCDF error, but instead indicates a system error occurred during a
netCDF call, such as writing a file too large for the file system.

> Looking at these files I found that there is a parameter called FILELONG that 
> is set to 2,147,483,647, and the program that I am running stop when the 
> output file reach 2,147,482,896, so is possible that this is my problem. I 
> modified this limit to 4 GB (also in the posixio.c file) and recompiled 
> netcdf 
> again, but the problem is still the same.
>
> I modified 5 files (where the FILELONG is):
> 
> ../src/libsrc/netcdf.h
> ../src/fortran/netcdf.inc
> ../include/netcdf.h
> ../include/netcdf.inc
> ../src/libsrc/posixio.c
> 
> My question is, am I missing something here?
> 
> How can I set netcdf to write a file longer than 2 GB?
> How can modify (increase) the number of open netcdf files (files and 
> parameters)

It doesn't help to modify FILELONG, that is not the problem.

The 2.147 Gbyte limit is as large as a file can be on systems that use
32-bit signed integers for file offsets.  In order for a file system
to support files larger than about 2 Gbytes, it may have to be
configured properly when you create the disk partition for the file
system.  You can test this by trying to write a larger file with a
simple program that doesn't use netCDF but just writes the same bytes
in a loop, to see if your file system supports large files.

Even if you have large file support in the file system, you may
still have to compile the netCDF library with the right flags to
permit large netCDF files (over 2Gbytes) to be written.  There are
examples in the installation instructions at

  http://www.unidata.ucar.edu/packages/netcdf/INSTALL.html

for Large File Support for IBM AIX, HPUX, IRIX64, Linux 2.4 on i686,
and Solaris/SPARC.  Other systems with Large File Support may work
similarly.

Also see the Frequently Asked Question on Large File Support in the
netCDF FAQ:

  http://www.unidata.ucar.edu/packages/netcdf/faq.html#lfs

which refers to a new "Large File Support" section in the User's Guide
that provides more details on constraints on writing netCDF files
larger than 2 Gbytes.

--Russ

_____________________________________________________________________

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