1. NetCDF 3.6: What’s New www.unidata.ucar.edu/packages/netcdf/ Russ Rew
Unidata Program Center
University Corporation for Atmospheric Research

2. Overview A new format variant Backward compatibility
Refactored documentation
File size limitations eliminated
Better configuration support
Better Windows support
Bug fixes, performance enhancements

3. Larger netCDF files, 64-bit file offsets
Current “classic” format uses 32-bit offsets
New 64-bit offset format mode available on creation, for very large files:
nc_create(file, NC_64BIT_OFFSET, &ncid)
Initial development by Greg Sjaardema, Sandia Labs
We added:
Fortran, C++, ncgen, ncdump support
Extensive additional error checking
2GiB to 4GiB variable size increase
Elimination of 4GiB record size limit

4. Backward Compatibility
Version 3.6 library reads classic format or new format transparently
By default, new files are created in classic format
New format should only be used for files too large for classic format
No code changes needed for existing code
Third-party software eventually should be upgraded to 3.6 to support new format

5. Refactored Documentation
User’s Guides for C, FORTRAN-77, FORTRAN-90 converted from FrameMaker (proprietary) to Texinfo (GNU documentation system)
Language-neutral User’s Guide documents data model and language-independent concepts
Language-specific guides for C, Fortran-77, Fortran-90, and C++ interfaces
Will support better maintenance of documentation, easier addition of other language-specific manuals

6. Elimination of some size limitations
I GiB = 230 or about bytes
I EiB = 260 or about bytes
Limit
Without Large File Support (LFS)
NetCDF 3.5 with LFS
NetCDF 3.6 with LFS, classic format
NetCDF 3.6 with LFS, 64-bit offset format
Maximum file size
2 GiB
8 EiB
Maximum size of fixed variable, record size of record variable
4 GiB
Maximum record size
2 GiB / nrecs
8 EiB / nrecs

7. Better configuration support
Upgraded to use latest autoconf configuration tool
Builds with Large File Support by default, if available
Tested on more platforms with more development environments

8. Better Windows support
Included with source distribution in win32 directory
Added .Net port
Builds with VC++.NET from source
Added windows installer files to build windows binary installs

9. Performance enhancements, bug fixes
Fortran -77 implementation upgraded with more recent cfortran.h
Added -x option to ncgen to use fast “no fill” mode for netcdf file creation
Fixed ncdump and ncgen to properly handle dimension lengths > 231
Added new error codes for invalid dimension and variable size
Added tests for invalid offsets in classic format
Added performance fix for Fortran-90 array access interfaces