Next: , Previous: Internationalization, Up: Common features


3.2 Metadata Optimization

Availability: ncatted, ncks, ncrename
Short options: None
Long options: ‘--hdr_pad’, ‘--header_pad
NCO supports padding headers to improve the speed of future metadata operations. Use the ‘--hdr_pad’ and ‘--header_pad’ switches to request that hdr_pad bytes be inserted into the metadata section of the output file. Future metadata expansions will not incur the performance penalty of copying the entire output file unless the expansion exceeds the amount of header padding exceeded. This can be beneficial when it is known that some metadata will be added at a future date.

This optimization exploits the netCDF library nc__enddef() function, which behaves differently with different versions of netCDF. It will improve speed of future metadata expansion with CLASSIC and 64bit netCDF files, but not necessarily with NETCDF4 files, i.e., those created by the netCDF interface to the HDF5 library (see Selecting Output File Format).