The SCA$GET_OCCURRENCE routine returns an occurrence from the
    query specified by the query_name argument.

    If the occurrence handle supplied is zero, the routine returns
    a handle to the first occurrence in the query represented by the
    argument query_name. If the occurrence handle supplied on input
    represents a valid occurrence, the routine returns a handle to
    the next occurrence in the query result. In order to be valid, the
    occurrence handle supplied on input must refer to an occurrence in
    the query represented by the argument query_name.

    The query name supplied is interpreted in the context of the
    command context identified by the argument command_context.

    Note that the order of retrieval of the occurrences is undefined.