Currently, the HDF5 capabilities of GNU Octave are very limited and are not generally useful for loading large HDF5 files from arbitrary sources. One of the most viable HDF5 Octave libraries has not been updated since 2015 and doesn’t work with recent Octave releases.

Basic HDF5 functionality

The HDF5 capabilities of Octave are not generally useful because the only way to load HDF5 files is to greedily load the entire file into a “struct” via the load() command. The save('-hdf5') command puts the HDF5 variables into an arbitrary group layout that may not be useful for your project.

NetCDF4

A possible alternative would be to use Octave NetCDF4. NetCDF4 is a subset of HDF5. Such a file format change would have to be with concurrence of others on your project.