memb_size is the size in bytes of each file member. Because this size is not saved in the file, it is used both for creating a new file, for re-opening and for extending an existing file.

When re-opening an existing family file, if there is only one member file, the library allows this memb_size to be bigger than or equal to the size of existing member file; if there are more than one member file, the library sets the memb_size to be equal to the size of first existing member file internally. In either case, no memb_size smaller than the size of existing member file is allowed. If this happens, the library will adjust the memb_size to the first existing member file size internally instead of returning error.

For example, if the total file size is 1MB and the only existing member file size is 1MB, memb_size can be bigger than or equal to 1MB. If the first member file size is 0.6MB and the second one is 0.4MB, the library will set memb_size to 0.6MB internally no matter what value the user passes in.

memb_fapl_id is the identifier of the file access property list to be used for each family member.

SUBROUTINE h5pset_fapl_family_f(prp_id, imemb_size, memb_plist, hdferr) 
  IMPLICIT NONE
  INTEGER(HID_T), INTENT(IN)   :: prp_id    ! Property list identifier
  INTEGER(HSIZE_T), INTENT(IN) :: memb_size ! Logical size, in bytes,
                                            ! of each family member
  INTEGER(HID_T), INTENT(IN) :: memb_plist  ! Identifier of the file 
                                            ! access property list to be
                                            ! used for each family member
  INTEGER, INTENT(OUT) :: hdferr            ! Error code
                                            ! 0 on success and -1 on failure
END SUBROUTINE h5pset_fapl_family_f