Queues a lock on a resource. The $ENQW service completes
    synchronously; that is, it returns to the caller when the
    lock has been either granted or converted. For asynchronous
    completion, use the Enqueue Lock Request ($ENQ) service; $ENQ
    returns to the caller after queuing the lock request, without
    waiting for the lock to be either granted or converted. In
    all other respects, $ENQW is identical to $ENQ. See the $ENQ
    description for all other information about the $ENQW service.

    The $ENQ, $ENQW, $DEQ, and $GETLKI services together provide the
    user interface to the Lock Management facility.

    On Alpha and Integrity server systems, this service accepts 64-
    bit addresses.

    Format

      SYS$ENQW  [efn] ,lkmode ,lksb ,[flags] ,[resnam] ,[parid]

                ,[astadr] ,[astprm] ,[blkast] ,[acmode] ,[rsdm_id]

    C Prototype

      int sys$enqw  (unsigned int efn, unsigned int lkmode,

                    struct _lksb *lksb, unsigned int flags,

                    void *resnam, unsigned int parid, void

                    (*astadr)(__unknown_params), unsigned __int64

                    astprm, void (*blkast)(__unknown_params),

                    unsigned int acmode, unsigned int rsdm_id,...);