Unable to enqueue lock.

  Explanation:  A lock required by RMU was not granted by the lock
  manager.

  User Action:  Refer to the secondary message to identify why the
  lock was not granted.  If the secondary message specifies a user
  correctable action (such as EXQUOTA), correct the  problem.   If
  the  secondary  message  specifies  an  internal  error (such as
  ACCVIO),  contact  your  Oracle   support   representative   for
  assistance.