Returns an occurrence from the query specified by the query_name
    argument.

    Format

      SCA$GET_OCCURRENCE  command_context,

                          query_name,

                          occurrence

1  –  Arguments

 command_context
    type:       $SCA_COMMAND_CONTEXT
    access:     read/write
    mechanism:  by reference

    An SCA command context.

 query_name
    type:       character string
    access:     read only
    mechanism:  by descriptor

    The name of the query in the context of the command context.

 occurrence
    type:       $SCA_HANDLE
    access:     read/write
    mechanism:  by reference

    An SCA occurrence handle that describes an occurrence.

2  –  Condition Values Returned

    SCA$_NORMAL           An occurrence has been successfully
                          returned.

    SCA$_NEWNAME          An occurrence has been successfully
                          returned. This occurrence has a different
                          name from the occurrence that was returned
                          by the previous call to this routine with
                          this query context. This condition implies
                          that this new occurrence is also of a
                          different symbol.

    SCA$_NEWITEM          An occurrence has been successfully
                          returned. This new occurrence is of a
                          different symbol from the occurrence that
                          was returned by the previous call to this
                          routine with this query context.

    SCA$_NOMORE           Warning. An occurrence has not been
                          returned. The traversal of the query result
                          has been exhausted.

3  –  Description

    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.