operation canceled

  Explanation:  The lock conversion request has been canceled, and
  the  lock  has  been  granted  at  its previous lock mode.  This
  condition value is returned under the following  conditions:   a
  lock  request results in queueing a lock conversion request, the
  request has not been  granted  yet  (it  is  in  the  conversion
  queue),  and,  in  the  interim, the unlock service is called to
  cancel  this  lock  conversion.   Note  that  if   the   waiting
  conversion  request is granted BEFORE the unlock call can cancel
  the conversion, the unlock call  returns  CANCELGRANT,  and  the
  conversion request returns NORMAL.

  User Action:  This error message indicates a possible  error  in
  the    locking   protocols.    Contact   your   Oracle   support
  representative for assistance.