4 File Structure and Performance
This chapter describes the file structure of a netCDF classic or
64-bit offset dataset in enough detail to aid in understanding netCDF
performance issues.
NetCDF is a data abstraction for array-oriented data access and a
software library that provides a concrete implementation of the
interfaces that support that abstraction. The implementation provides
a machine-independent format for representing arrays. Although the
netCDF file format is hidden below the interfaces, some understanding
of the current implementation and associated file structure may help
to make clear why some netCDF operations are more expensive than
others.
Knowledge of the format is not needed for reading and writing netCDF
data or understanding most efficiency issues. Programs that use only
the documented interfaces and that make no assumptions about the
format will continue to work even if the netCDF format is changed in
the future, because any such change will be made below the documented
interfaces and will support earlier versions of the netCDF file
format.
