Before calling LBR$GET_RECORD, you must first call LBR$LOOKUP_
    KEY or LBR$FIND to set the internal library read context to the
    record's file address (RFA) of the module header of the module
    whose records you want to read.

    LBR$GET_RECORD uses two record access modes: locate mode and
    move mode. Move mode is the default. The LBR$SET_LOCATE and
    LBR$SET_MOVE subroutines set these modes. The record access
    modes are mutually exclusive; that is, when one is set, the other
    is turned off. If move mode is set, LBR$GET_RECORD copies the
    record to the user-specified buffer described by inbufdes. If you
    have optionally specified the output buffer string descriptor,
    outbufdes, the Librarian fills it with the actual length and
    address of the data. If locate mode is set, LBR$GET_RECORD
    returns the record by way of an internal subroutine buffer,
    pointing the outbufdes descriptor to the internal buffer. The
    second parameter, inbufdes, is not used when locate mode is set.