Use the LBR$FIND routine to access a module that you had accessed
    earlier in your program. For example, if you look up several
    keys with LBR$LOOKUP_KEY, you can save the RFAs returned by
    LBR$LOOKUP_KEY and later use LBR$FIND to reaccess the modules.
    Thus, you do not have to look up the module header's key every
    time you want to access the module. If the specified RFA is
    valid, LBR$FIND initializes internal tables so you can read the
    associated data.