library_index

    OpenVMS usage:longword_unsigned
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference
    Library control index returned by the LBR$INI_CONTROL routine.
    The library_index argument is the address of the longword that
    contains the index.

 block_type

    OpenVMS usage:longword_unsigned
    type:         longword (unsigned)
    access:       read only
    mechanism:    by value
    Extent of the flush operation. The block_type argument contains
    the longword value that indicates how the flush operation
    proceeds. If you specify LBR$C_FLUSHDATA, the data blocks are
    flushed. If you specify LBR$C_FLUSHALL, first the data blocks and
    then the current library index are flushed.

    Each programming language provides an appropriate mechanism for
    accessing these symbols.