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There are several exceptions to the above file closing rule. One is when the H5close function is used instead of H5Fclose. H5close causes a general shut down of the library: all data is written to disk, all identifiers are closed, and all memory used by the library is cleaned up. Another exception occurs on parallel processing systems. Suppose on a parallel system an application has opened a file, a group in the file, and two datasets in the group. If the application uses the H5Fclose function to close the file, the call will fail with an error. The open group and datasets must be closed before the file can be closed. A third exception is when the file access property list includes the property H5F_CLOSE_STRONG. This property causes the closing of all of the file’s open items when the file is closed with H5Fclose. For more information about H5close, H5Fclose, and H5Pset_fclose_degree, see the HDF5 Reference Manual

The reference manual entries for functions that return identifiers describe what might be returned as follows:

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